<SEC-DOCUMENT>0001193125-24-228326.txt : 20241108
<SEC-HEADER>0001193125-24-228326.hdr.sgml : 20241108
<ACCEPTANCE-DATETIME>20240930060659
<PRIVATE-TO-PUBLIC>
ACCESSION NUMBER:		0001193125-24-228326
CONFORMED SUBMISSION TYPE:	CORRESP
PUBLIC DOCUMENT COUNT:		2
FILED AS OF DATE:		20240930

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Upstream Bio, Inc.
		CENTRAL INDEX KEY:			0002022626
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		ORGANIZATION NAME:           	03 Life Sciences
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		CORRESP

	BUSINESS ADDRESS:	
		STREET 1:		890 WINTER STREET, SUITE 200
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451
		BUSINESS PHONE:		781-208-2466

	MAIL ADDRESS:	
		STREET 1:		890 WINTER STREET, SUITE 200
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451
</SEC-HEADER>
<DOCUMENT>
<TYPE>CORRESP
<SEQUENCE>1
<FILENAME>filename1.htm
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<TITLE>CORRESP</TITLE>
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</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September&nbsp;30, 2024 </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><U>FOIA CONFIDENTIAL TREATMENT REQUESTED </U></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The entity
requesting confidential treatment is </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Upstream Bio, Inc. </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">890
Winter Street, Suite 200 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Waltham, MA 02451 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Telephone: (781)
<FONT STYLE="white-space:nowrap">208-2466</FONT> </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman"><B>CERTAIN PORTIONS OF THIS LETTER HAVE BEEN OMITTED FROM THE VERSION FILED VIA EDGAR.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS. INFORMATION THAT WAS OMITTED IN THE EDGAR VERSION HAS BEEN NOTED IN THIS LETTER WITH A PLACEHOLDER IDENTIFIED BY THE MARK &#147;[***].&#148; </B></P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><U>VIA EDGAR </U></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">100 F Street, N.E. </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Washington, D.C. 20549 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Attention: Chris Edwards, Jimmy McNamara, Kevin Kuhar and Franklin Wyman </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>RE: Upstream Bio, Inc. </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Registration Statement on <FONT
STYLE="white-space:nowrap">Form&nbsp;S-1</FONT></B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>File <FONT STYLE="white-space:nowrap">No.&nbsp;333-282197</FONT> </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>CIK No.&nbsp;0002022626 </B></P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><U>Rule 83 Confidential
Treatment Request by Upstream Bio, Inc. </U></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Dear Ladies and Gentlemen: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On behalf of Upstream Bio, Inc. (the &#147;Company&#148;), in response to comments from the staff (the &#147;Staff&#148;) of the U.S. Securities and Exchange
Commission (the &#147;Commission&#148;) received by letter dated July&nbsp;9, 2024 (the &#147;Comment Letter&#148;) relating to the Company&#146;s Registration Statement on Form <FONT STYLE="white-space:nowrap">S-1,</FONT> originally confidentially
submitted to the Commission on June&nbsp;12, 2024, and subsequently publicly filed by the Company with the Commission on September&nbsp;18, 2024 (File <FONT STYLE="white-space:nowrap">No.&nbsp;333-282197)</FONT> (the &#147;Registration
Statement&#148;), we submit this supplemental letter to address comment 14 of the Comment Letter. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED
BY UPSTREAM BIO, INC. </B></P>
</DIV></Center>


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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 2
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Because of the commercially sensitive nature of information contained herein, this submission is accompanied
by the Company&#146;s request for confidential treatment for selected portions of this letter. The Company has concurrently filed a separate letter with the Office of Freedom of Information and Privacy Act Operations in connection with the
confidential treatment request, pursuant to Rule 83 of the Commission&#146;s Rules on Information and Requests, 17 C.F.R. &#167; 200.83. For the Staff&#146;s reference, we have enclosed a copy of the Company&#146;s letter to the Office of Freedom of
Information and Privacy Act Operations. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We confirm on behalf of the Company that, prior to circulating copies of the preliminary prospectus in connection
with the offering, the Company will file a <FONT STYLE="white-space:nowrap">pre-effective</FONT> amendment to the Registration Statement that will include all information other than information that may be excluded in reliance upon Rule 430A of
Regulation C, and the final price range to be included in such amendment which will comply with the Staff&#146;s interpretation regarding the parameters of a <I>bona fide </I>price range. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Prior to the effectiveness of the Registration Statement, the Company intends to implement a reverse stock split of its common stock (the &#147;Stock
Split&#148;). The Company expects to reflect the Stock Split in a <FONT STYLE="white-space:nowrap">pre-effective</FONT> amendment to the Registration Statement that includes the actual price range. For purposes of this letter, we have presented all
dollar and per share amounts without giving effect to the Stock Split to be consistent with the current presentation in the Registration Statement. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>The Company respectfully requests that the bracketed information contained in this letter be treated as confidential information pursuant to Rule 83
promulgated by the Commission, 17 C.F.R. &#167;200.8, and that the Commission provide timely notice to E. Rand Sutherland and Michael Gray before it permits any disclosure of the bracketed information in this letter. </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">For the convenience of the Staff, we have recited the prior comment from the Staff in the Comment Letter in italicized type and have followed the comment with
the Company&#146;s response. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD WIDTH="5%" VALIGN="top" ALIGN="left"><I>14.</I></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><I>Once you have an estimated offering price range, please explain to us the reasons for any differences
between recent valuations of your common stock leading up to the planned offering and the midpoint of your estimated offering price range. This information will facilitate our review of your accounting for stock compensation.
</I></P></TD></TR></TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company respectfully submits the below additional information to assist the Staff in its review of the Company&#146;s position
with respect to its determination of the fair value of the Company&#146;s common stock, par value $0.001 per share (&#147;Common Stock&#148;), underlying its outstanding equity awards and the reasons for the differences between the recent valuation
of its Common Stock and the estimated offering price for its initial public offering (&#147;IPO&#148;). </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">2 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

</DIV></Center>


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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 3
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Preliminary IPO Price Range </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company advises the Staff that it estimates a preliminary price range of approximately $[***] to $[***] per share (the &#147;Preliminary Price Range&#148;)
for its IPO, before giving effect to the Stock Split, resulting in a midpoint of the Preliminary Price Range of $[***] per share. The actual price range to be included in a subsequent amendment to the Registration Statement (which will comply with
the Staff&#146;s interpretation regarding the parameters of a <I>bona fide</I> price range) has not yet been determined and remains subject to adjustment based on factors outside of the Company&#146;s control. However, the Company believes that the
foregoing Preliminary Price Range will not be subject to significant change. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Determining the Fair Value of Common Stock Prior to the IPO </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As there has been no public market for the Common Stock to date, the estimated fair value of its Common Stock has been determined by the Company&#146;s board
of directors (the &#147;Board&#148;) as of the date of each equity award, with input from management, considering the Company&#146;s most recently available third-party valuations of its Common Stock, and the Board&#146;s assessment of additional
objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent valuation through the date of the grant. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company&#146;s most recent third-party valuations of its Common Stock utilized by the Board in determining exercise prices at the time of each equity award
were as follows: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD VALIGN="bottom" NOWRAP> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman">Date of</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman">Third-Party</P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1.00pt solid #000000; display:table-cell; font-size:8pt; font-family:Times New Roman; ">Valuation</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000">Date of<br>Board&nbsp;Approval</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000">Estimated<br>Fair&nbsp;Market&nbsp;Value<br>of Common Stock<br>per Share</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">October&nbsp;31, 2022</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">December&nbsp;7,&nbsp;2022</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.48</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">February&nbsp;17, 2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">March&nbsp;2, 2023</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.47</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">June&nbsp;6, 2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">June&nbsp;10, 2023</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">March&nbsp;1, 2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">March&nbsp;13, 2024</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.96</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">April&nbsp;22, 2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">April&nbsp;25, 2024</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.91</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">May&nbsp;20, 2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">June&nbsp;11, 2024</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$9.59</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">July&nbsp;19, 2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">July&nbsp;31, 2024</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$11.14</TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">3 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

</DIV></Center>


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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 4
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Equity Awards Between January&nbsp;1, 2023 and September 30, 2024 </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The following table summarizes by grant date the number of shares subject to awards granted between January&nbsp;1, 2023 and September&nbsp;30, 2024, the per
share exercise price of the awards and the fair value of Common Stock underlying the awards on each grant date: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD VALIGN="bottom" NOWRAP> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; display:table-cell; font-size:8pt; font-family:Times New Roman; ">Grant Date</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000">Type&nbsp;of<BR>Award</TD>
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<TD VALIGN="bottom" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000">Number&nbsp;of<BR>Shares&nbsp;Subject<BR>to Awards<BR>Granted</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000">Per&nbsp;Share<br>Exercise<BR>Price<br>of Award</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000">Per&nbsp;Share<br>Fair&nbsp;Value<br>of&nbsp;Common&nbsp;Stock<br>on Grant Date</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000">Per&nbsp;Share<br>Estimated&nbsp;Fair<BR>Value&nbsp;of&nbsp;Award<br>on&nbsp;Grant&nbsp;Date<SUP STYLE="font-size:75%; vertical-align:top">(1)</SUP></TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">01/06/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">14,000</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.48</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.48</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$2.45</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">03/02/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">45,585</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.47</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.47</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.17</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">03/03/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">553,430</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.47</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.47</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.17</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">03/14/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">34,870</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.47</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.47</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.17</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">04/08/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">42,918</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.47</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.47</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$2.98</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">06/12/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">40,235</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.42</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">07/18/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">80,471</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.37</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">08/09/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">24,141</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.31</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">08/10/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">33,900</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.31</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">08/14/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">287,500</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.31</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">08/15/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">10,729</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.31</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">09/06/2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">48,282</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.40</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">03/27/2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">742,581</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.96</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.96</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$3.41</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">04/04/2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">826,220</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.96</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$5.96</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.20</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">04/25/2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">1,004,575</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.91</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.91</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.87</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">05/02/2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">310,600</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.91</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.91</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.78</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">05/05/2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">108,250</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.91</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.91</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.78</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">05/07/2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">12,000</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.91</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.91</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$4.78</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">06/11/2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">9,000</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$9.59</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$9.59</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.81</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">06/19/2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">12,000</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$9.59</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$9.59</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$6.80</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">07/31/2024</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">Option</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">34,000</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$11.14</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$11.14</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center">$8.60</TD></TR>
</TABLE> <P STYLE="line-height:8.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000;width:11%">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(1)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">The per share estimated fair value of options reflects the fair value of options granted on each grant date
determined using the Black-Scholes option-pricing model. </P></TD></TR></TABLE> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Valuation Methodologies </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The third-party valuations were performed in accordance with the guidance outlined in the American Institute of Certified Public Accountants&#146; Accounting
and Valuation Guide, <I>Valuation of Privately-Held-Company Equity Securities Issued as Compensation</I> (the &#147;Practice Aid&#148;). As disclosed in the Registration Statement, the Company&#146;s enterprise value valuations were prepared using
either an option pricing method (&#147;OPM&#148;) market-adjusted back-solve approach based on a recent arms-length transaction, a market-adjusted equity, or a hybrid method (&#147;Hybrid&#148;), which is a combination of an OPM scenario and one or
more scenarios using a probability-weighted expected return method (&#147;PWERM&#148;), with an IPO scenario and a sale scenario. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">4 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

</DIV></Center>


<p style="margin-top:1em; margin-bottom:0em; page-break-before:always"> </p>
<HR SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 5
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The OPM treats common stock and preferred stock as call options on the total equity value of a Company, with
exercise prices based on the value thresholds at which the allocation among the various holders of a company&#146;s securities changes. Under this method, the common stock has value only if the funds available for distribution to stockholders
exceeded the value of the preferred stock liquidation preferences at the time of the liquidity event, such as a strategic sale or a merger. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The PWERM is
a scenario-based methodology that estimates the fair value of common stock based upon an analysis of future values for the company, assuming various outcomes. The common stock value is based on the probability-weighted present value of expected
future investment returns considering each of the possible outcomes available as well as the rights of each class of stock. The future value of the common stock under each outcome is discounted back to the date of the applicable valuation (each, a
&#147;Valuation Date&#148;) at an appropriate risk-adjusted discount rate and probability weighted to arrive at an indication of value for the common stock. A discount for lack of marketability (&#147;<U>DLOM</U>&#148;) of the common stock is then
applied to arrive at an indication of value for the common stock. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The hybrid method is a hybrid between the PWERM and OPM, estimating the
probability-weighted value across multiple scenarios, but using the OPM to estimate the allocation of value within one or more of those scenarios. When using the hybrid method, the third-party valuations considered two future-event scenarios: an IPO
scenario and a sale scenario. The equity value of the Company in the IPO scenario was determined using a market approach. The IPO scenario assumed that all shares of redeemable convertible preferred stock would convert into shares of Common Stock
and would no longer have the liquidation preferences and preferential rights attributable to the redeemable convertible preferred stock as compared to the Common Stock prior to the IPO. The guideline initial public offering transactions in the IPO
scenario consist of biotechnology companies with recent initial public offerings. The valuation converted the Company&#146;s estimated future value in an IPO to present value using a risk-adjusted discount rate. The equity value for the sale
scenario was estimated using the price of a recently issued preferred security or a market-adjusted equity approach. At certain Valuation Dates, a preferred tranche model was used (time-based call option or milestone-based model) as appropriate at
each respective Valuation Date. The valuation utilized an OPM to quantify or attribute value to these economic rights of redeemable convertible preferred stock as compared to the Common Stock, such as liquidation preferences, dividend provisions,
and participation rights after liquidation preferences. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I><U>October&nbsp;31, 2022 Valuation </U></I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of the Common Stock of $3.48 per share at October&nbsp;31, 2022 was determined with the assistance of an independent third-party valuation firm
and approved by the Board on December&nbsp;7, 2022. This valuation was used to support the fair market value of the Common Stock in accordance with Section&nbsp;409A of the IRC with respect to options granted on January&nbsp;6, 2023, along with
other factors determined by the Board to be relevant at the time of such grant of options. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">5 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 6
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The October&nbsp;31, 2022 valuation applied the OPM to allocate the fair value of the Company&#146;s equity
to various securities within the Company&#146;s capital structure. Under this method, the OPM model was built based on the Company&#146;s capital structure and reasonable option model inputs. The total equity value of the Company was determined
based on a market-adjusted approach. Under this approach, the Company&#146;s equity value from the prior valuation of June&nbsp;30, 2022 was adjusted based on consideration given to the performance of the biotechnology indices as well as the
Company&#146;s entity-specific factors. The valuation also considered the Series&nbsp;A redeemable convertible preferred stock (the &#147;Series&nbsp;A Preferred&#148;) investor right to purchase additional future Series A Preferred shares at one
additional milestone tranche closing. The 35.0% DLOM applied to the fair value of Common Stock was estimated using a put option analysis. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The principal
factor that contributed to the increase in the fair value of the Common Stock from June 30, 2022, the date of the Company&#146;s most recent valuation, to October&nbsp;31, 2022 included the following: </P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">A market adjustment factor of 3.6% was applied as of the Valuation Date to reflect the improved market conditions
within the biotechnology indices over the measurement period. </P></TD></TR></TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Between October&nbsp;31, 2022 and February&nbsp;17, 2023, the Company
continued to operate its business in the ordinary course and there were no significant developments in its business. As a result, the Company determined that no developments that would affect the valuation occurred from October&nbsp;31, 2022 to
February&nbsp;17, 2023. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I><U>February&nbsp;17, 2023 Valuation </U></I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of the Common Stock of $4.47 per share at February&nbsp;17, 2023 was determined with the assistance of an independent third-party valuation firm
and approved by the Board on March&nbsp;2, 2023. This valuation was used to support the fair market value of the Common Stock in accordance with Section&nbsp;409A of the IRC with respect to options granted on March&nbsp;2, 2023, March&nbsp;3, 2023,
March&nbsp;14, 2023 and April&nbsp;8, 2023, along with other factors determined by the Board to be relevant at the time of each such grant of options. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">6 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 7
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The February&nbsp;17, 2023 valuation applied the OPM method to allocate the fair value of the Company&#146;s
equity to various securities within the Company&#146;s capital structure. Under this method, the OPM model was built based on the Company&#146;s capital structure and reasonable option model inputs. The total equity value of the Company was
calibrated based on the implied value of the Series A Preferred upon achievement of the milestone in February 2023, which resulted in the second tranche closing of Series A Preferred. This implied total equity value was adjusted to reflect market
condition changes observed in the biotechnology indices over the measurement period of October 2021 through the Valuation Date. The 35.0% DLOM applied to the fair value of Common Stock was estimated using a put option analysis. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The principal factors that contributed to the increase in the fair value of the Common Stock from October&nbsp;31, 2022 to February&nbsp;17, 2023 include the
following: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The Company was able to achieve development milestones during the measurement period. The achievement of specific
research milestones as outlined in the Series A Stock Purchase Agreement triggered the settlement of the second tranche closing of Series A Preferred in February 2023. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The completion of the second tranche milestone events and second tranche closing of the Series A Preferred
resulted in an appreciation to the fair value of the total equity of the Company. </P></TD></TR></TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Between February&nbsp;17, 2023 and June&nbsp;6, 2023,
the Company continued to operate its business in the ordinary course and there were no significant developments in its business. As a result, the Company determined that no developments that would affect the valuation occurred from February&nbsp;17,
2023 to June&nbsp;6, 2023. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I><U>June&nbsp;6, 2023 Valuation </U></I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of the Common Stock of $5.10 per share at June&nbsp;6, 2023 was determined with the assistance of an independent third-party valuation firm and
approved by the Board on June&nbsp;10, 2023. This valuation was used to support the fair market value of the Common Stock in accordance with Section&nbsp;409A of the IRC with respect to options granted on June&nbsp;12, 2023, July&nbsp;18, 2023,
August&nbsp;9, 2023, August&nbsp;10, 2023, August&nbsp;14, 2023, August&nbsp;15, 2023 and September&nbsp;6, 2023, along with other factors determined by the Board to be relevant at the time of each such grant of options. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The June&nbsp;6, 2023 valuation applied the OPM method to allocate the fair value of the Company&#146;s equity to various securities within the Company&#146;s
capital structure. Under this method, the OPM model was built based on the Company&#146;s capital structure and reasonable option model inputs. The equity value of the Company was determined such that the implied value per share of Series&nbsp;B
redeemable convertible preferred stock (the &#147;Series B Preferred&#148;) is equal to its original issue price, which included the initial Series&nbsp;B Preferred closing in June 2023 plus the future call option right of Series B Preferred
investors to purchase additional shares at one additional tranche closing. The 30.0% DLOM applied to the fair value of Common Stock was estimated using a put option analysis. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">7 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 8
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The principal factors that contributed to the increase in the fair value of the Common Stock from
February&nbsp;17, 2023 to June&nbsp;6, 2023 include the following: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The appreciation of Common Stock as a result of a new preferred round of financing from outside investors as of
the Valuation Date. </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The DLOM was reduced from 35% to 30% during the measurement period. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Between June&nbsp;6, 2023 and March&nbsp;1, 2024, the Company continued to operate its business in the ordinary course and there were no significant
developments in its business. As a result, the Company determined that no developments that would affect the valuation occurred from June&nbsp;6, 2023 to March&nbsp;1, 2024. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I><U>March&nbsp;1, 2024 Valuation </U></I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of
the Common Stock of $5.96 per share at March&nbsp;1, 2024 was determined with the assistance of an independent third-party valuation firm and approved by the Board on March&nbsp;13, 2024. This valuation was used to support the fair market value of
the Common Stock in accordance with Section&nbsp;409A of the IRC with respect to options granted on March&nbsp;27, 2024 and April&nbsp;4, 2024, along with other factors determined by the Board to be relevant at the time of each such grant of
options. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The March&nbsp;1, 2024 valuation applied the OPM method to allocate the fair value of the Company&#146;s equity to various securities within the
Company&#146;s capital structure. Under this method, the OPM model was built based on the Company&#146;s capital structure and reasonable option model inputs. The total equity value of the Company was determined based on a market-adjusted approach.
Under this approach, the Company&#146;s equity value from the prior valuation was adjusted based on consideration given to the performance of the biotechnology indices as well as the Company&#146;s entity-specific factors. The valuation also
considered the Series B Preferred investors right to purchase additional future Series B Preferred shares at one additional tranche closing. The 35.0% DLOM applied to the fair value of Common Stock was estimated using a put option analysis. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The principal factor that contributed to the increase in the fair value of the Common Stock from June&nbsp;6, 2023 to March&nbsp;1, 2024 was: </P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The Company continued ongoing research and development efforts over the measurement period. The market-adjusted
total equity approach applied a venture capital rate of return to the operational expenses to reflect the general business progression over the measurement period. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Between March&nbsp;1, 2024 and April&nbsp;22, 2024, the Company continued to operate its business in the ordinary course and there were no significant
developments in its business. As a result, the Company determined that no developments that would affect the valuation occurred from March&nbsp;1, 2024 to April&nbsp;22, 2024. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">8 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
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 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I><U>April&nbsp;22, 2024 Valuation </U></I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of the Common Stock of $6.91 per share at April&nbsp;22, 2024 was determined with the assistance of an independent third-party valuation firm
and approved by the Board on April&nbsp;25, 2024. This valuation was used to support the fair market value of the Common Stock in accordance with Section&nbsp;409A of the IRC with respect to options granted on April&nbsp;25, 2024, May&nbsp;2, 2024,
May&nbsp;5, 2024 and May&nbsp;7, 2024, along with other factors determined by the Board to be relevant at the time of each such grant of options. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The
April&nbsp;22, 2024 valuation was prepared using a Hybrid method with considerations of both an OPM and a PWERM approach, which included IPO and sale scenarios that were probability weighted based on their expected likelihoods of occurring. The IPO
scenario was assigned a probability weight of 5.0%, which considered guideline IPO transactions identified within the last several years and the Company&#146;s progress toward an IPO. The Common Stock value in the IPO scenario was adjusted by a DLOM
of 9.5%. The Company&#146;s sale scenario under an OPM method to allocate the fair value of the Company&#146;s equity to various securities within the Company&#146;s capital structure was assigned a probability weight of 95.0% and reflected a market
adjustment based on the performance of biotechnology indices to the Company&#146;s equity value, which was based on the Series B Preferred second tranche closing in April 2024. A 35% DLOM was applied in the sale scenario. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The principal factors that contributed to the increase in the fair value of the Common Stock from March&nbsp;1, 2024 to April&nbsp;22, 2024 include the
following: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The progression of the Company towards an IPO, including the Company&#146;s IPO organizational meeting held on
May&nbsp;8, 2024, resulted in an appreciated Common Stock valuation as a near-term IPO scenario was considered as of the Valuation Date. </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The settlement of the Series B Preferred second tranche in April 2024. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Between April&nbsp;22, 2024 and May&nbsp;20, 2024, the Company continued to operate its business in the ordinary course and there were no significant
developments in its business. As a result, the Company determined that no developments that would affect the valuation occurred from April&nbsp;22, 2024 to May&nbsp;20, 2024. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I><U>May&nbsp;20, 2024 Valuation </U></I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of the
Common Stock of $9.59 per share at May&nbsp;20, 2024 was determined with the assistance of an independent third-party valuation firm and approved by the Board on June&nbsp;11, 2024. This valuation was used to support the fair market value of the
Common Stock in accordance with Section&nbsp;409A of the IRC with respect to options granted on June&nbsp;11, 2024 and June&nbsp;19, 2024, along with other factors determined by the Board to be relevant at the time of each such grant of options.
</P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">9 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 10
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The May&nbsp;20, 2024 valuation utilized the hybrid method with consideration of both an OPM and a PWERM,
which included IPO and sale scenarios that were probability weighted based on their expected likelihoods of occurring. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The PWERM used in the May&nbsp;20,
2024 valuation included the IPO scenario and the sale scenario. The IPO scenario was assigned a probability weight of 25.0%, which considered guideline IPO transactions identified within the last several years and the Company&#146;s progress toward
an IPO, as adjusted by a DLOM of 9.0%. The Company&#146;s sale scenario was assigned a probability weight of 75.0% and reflected the market adjustment to the Company&#146;s equity value since April&nbsp;22, 2024 based on consideration given to the
performance of the biotechnology indices as well as the Company&#146;s entity-specific factors. A DLOM of 31.0% was then applied to arrive at an indication of value for the Common Stock under the sale scenario. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The principal factors that contributed to the increase in the fair value of the Common Stock from April&nbsp;22, 2024 to May&nbsp;20, 2024 include the
following: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The progression of the Company towards an IPO, including the expected confidential submission of the
Company&#146;s initial draft registration statement on Form <FONT STYLE="white-space:nowrap">S-1</FONT> to the Commission, resulted in an increase scenario weighting applied to a near-term IPO scenario as of the Valuation Date.
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Given the progression of the Company towards a potential IPO event, the DLOM applied in the IPO scenario was
reduced to 9.0%. </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The sale scenario DLOM was also reduced from 35.0% to 31.0% as of the Valuation Date. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Between May&nbsp;20, 2024 and July&nbsp;19, 2024, the Company continued to operate its business in the ordinary course and there were no significant
developments in its business. As a result, the Company determined that no developments that would affect the valuation occurred from May&nbsp;20, 2024 to July&nbsp;19, 2024. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I><U>July&nbsp;19, 2024 Valuation </U></I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of
the Common Stock of $11.14 per share at July&nbsp;19, 2024 was determined with the assistance of an independent third-party valuation firm and approved by the Board on July&nbsp;31, 2024. This valuation was used to support the fair market value of
the Common Stock in accordance with Section&nbsp;409A of the IRC with respect to options granted on July&nbsp;31, 2024, along with other factors determined by the Board to be relevant at the time of such grant of options. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">10 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 11
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The July&nbsp;19, 2024 valuation utilized the hybrid method of both the OPM and a PWERM, which included IPO
and sale scenarios that were probability weighted based on their expected likelihoods of occurring. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The PWERM used in the July&nbsp;19, 2024 valuation
included the IPO scenario and the sale scenario. The IPO scenario was assigned a probability weight of 35.0%, which considered guideline IPO transactions identified within the last several years and the Company&#146;s progress toward an IPO, as
adjusted by a DLOM of 7.0%. The Company&#146;s sale scenario was assigned a probability weight of 65.0% and reflected the market adjustment to the Company&#146;s equity value since May&nbsp;20, 2024 based on consideration given to the performance of
guideline public companies and the biotechnology indices as well as the Company&#146;s entity-specific factors. A DLOM of 30.0% was then applied to arrive at an indication of value for the Common Stock under the sale scenario. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The principal factors that contributed to the increase in the fair value of the Common Stock from May&nbsp;20, 2024 to July&nbsp;19, 2024 was the increase in
the probability weighting of the IPO scenario to 35.0%, reflecting progress made by the Company since May&nbsp;20, 2024, including the following: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">On June&nbsp;12, 2024, the Company confidentially submitted its initial draft registration statement on Form <FONT
STYLE="white-space:nowrap">S-1</FONT> to the Commission, for which it received its first comment letter on July&nbsp;9, 2024, and confidentially submitted an amendment on July&nbsp;18, 2024; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The Company, in consultation with its Board and the underwriters of the potential IPO, further solidified its
current plans for an IPO to be consummated in 2024, pending market conditions and review by the Commission, including incurring additional professional advisor fees, hiring additional employees to support the Company&#146;s organizational growth,
and otherwise preparing <FONT STYLE="white-space:nowrap">for&nbsp;post-IPO&nbsp;operations;</FONT> and </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Given the progression of the Company towards a potential IPO event the DLOM applied in IPO scenario was reduced
to 7.0% as of the Valuation Date. </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The sale scenario DLOM was also reduced from 31.0% to 30.0% as of the Valuation Date. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Between July&nbsp;19, 2024 and July&nbsp;31, 2024, the Company continued to operate its business in the ordinary course and there were no significant
developments in its business. Given minimal changes in the guideline public peers stock prices, biotechnology indices and overall market conditions, the Board determined that the key assumptions used in the July&nbsp;19, 2024 valuation were still
accurate as of July&nbsp;31, 2024 when it granted 34,000 options. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company does not intend to grant any additional equity awards under the existing
2021 Stock Option and Grant Plan leading up to the completion of the proposed IPO, assuming the Company&#146;s current timeline. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">11 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 12
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Comparison of Most Recent Valuation and the Preliminary Price Range </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As is typical in IPOs, the Preliminary Price Range was not derived using a formal quantitative determination of fair value, but was determined based on
discussions between the Company and the underwriters. Prior to September&nbsp;20, 2024, the Company and the underwriters had not had any specific discussions regarding the Preliminary Price Range. Among the factors that were considered in setting
the Preliminary Price Range were the following: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the general conditions of the securities market and the recent market prices of, and the demand for, publicly
traded common stock of comparable companies; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the Company&#146;s financial condition and prospects; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">estimates of business potential and earnings prospects for the Company and the industry in which it operates;
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">valuations metrics for and recent performance of initial public offerings of companies in the biotechnology
sector; and </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">progress and stage of development of the Company&#146;s development programs. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In addition, the Company believes that the difference between the July&nbsp;19, 2024 fair value determination of $11.14 per share, which does not reflect the
anticipated Stock Split, and the Preliminary Price Range of $[***] to $[***] per share is the result of the factors above and the following factors and continued positive developments with respect to the Company&#146;s business that occurred
subsequent to July&nbsp;19, 2024, the date of the Company&#146;s most recent determination of the fair value of its Common Stock: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The Preliminary Price Range is based only upon a scenario in which the Company completes the IPO and is not
probability weighted, in contrast to the Company&#146;s third-party valuation of the Common Stock as of July&nbsp;19, 2024. Specifically, in the third-party valuation, the probability weighting for the IPO scenario was 35%. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The Preliminary Price Range necessarily assumes that the IPO has occurred and that a public market for the Common
Stock has been created, and, therefore, it excludes any DLOM of the Common Stock, which was taken into account in the third-party valuation as of July&nbsp;19, 2024. The DLOM in the valuation that was applied to the IPO scenario was 7.0%.
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The Preliminary Price Range assumes the conversion of all of the Company&#146;s outstanding redeemable
convertible preferred stock. The Company&#146;s redeemable convertible preferred stock currently has substantial economic rights and preferences over the Common Stock. Upon the closing of the IPO, all outstanding shares of the Company&#146;s
redeemable convertible preferred stock will convert into Common Stock, thus eliminating the superior rights and preferences of the redeemable convertible preferred stock as compared to the Common Stock. </P></TD></TR></TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">12 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 13
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>

<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Since July&nbsp;31, 2024, the last date on which the Company referenced the July&nbsp;19, 2024 third-party
valuation in connection with option grants, the Company has taken several steps toward the completion of an IPO, including completing <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">testing-the-waters</FONT></FONT> meetings and
publicly filing the Registration Statement with the Commission on September&nbsp;18, 2024. </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The valuations of comparable companies that have completed or launched IPOs from January 2024 to date, which
valuations reflected increases from the last rounds of private equity financing prior to such IPOs, i.e., reflecting <FONT STYLE="white-space:nowrap">step-up</FONT> multiples in the IPO. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
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<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">From June 2024 to September 2024, the Company conducted 70 <FONT STYLE="white-space:nowrap"><FONT
STYLE="white-space:nowrap">&#147;testing-the-waters&#148;</FONT></FONT> meetings with prospective investors, and as a result, the Company elected to continue to pursue an IPO. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The IPO market for biotechnology IPOs has exhibited momentum and increased strength, including four biotechnology
IPOs that were completed from July&nbsp;19, 2024 through September&nbsp;12, 2024, of which a majority priced at or above the <FONT STYLE="white-space:nowrap">mid-point</FONT> of the price range included in the respective preliminary prospectuses.
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The price that investors are willing to pay in the IPO, for which the Preliminary Price Range is intended to
serve as an estimate, may take into account other factors that have not been expressly considered in prior valuations of the Company&#146;s Common Stock, but the Company or the underwriters for the offering believe are significant to investors in
their own subjective and qualitative assessment of the Company, and thus may not be objectively determinable or quantifiable under the above-described valuation models. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">In determining the Preliminary Price Range, the underwriters utilized a number of valuation methodologies,
including a discounted cash flow analysis, factors likely to affect the Company&#146;s revenues and profitability, and relevant trading multiples for comparable public companies. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">The successful completion of the IPO would strengthen the Company&#146;s balance sheet, provide access to public
equity and provide enhanced operational flexibility, increasing the value of the Common Stock compared to that of a private company. </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Recent market conditions used in the determination of the Preliminary Price Range after discussions with the
underwriters, based on the current market environment and the supply and demand for such investment opportunities in the marketplace. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company believes the Preliminary Price Range for the IPO is reasonable. The Company also refers you to the discussion of its general approach of
determining fair value of equity awards set forth in the Registration Statement under the heading &#147;<I>Management</I><I>&#146;</I><I>s Discussion and Analysis of Financial Condition and Results of Operations&#151;Critical Accounting Estimates
and Significant Judgments&#151;Stock-Based Compensation&#151;Determination of Fair Value of Common Stock</I>&#148; for additional background regarding its equity grant valuation methodologies to date. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">13 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

</DIV></Center>


<p style="margin-top:1em; margin-bottom:0em; page-break-before:always"> </p>
<HR SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Office of Life Sciences </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">September 30, 2024 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
 14
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Because of the financially sensitive nature of the estimated price range, the Company requests confidential
treatment under 17 C.F.R. &#167;&nbsp;200.83 of the contents of this letter and has submitted a separate request for confidential treatment in accordance therewith to the Commission&#146;s Office of Freedom and Information Privacy Act Operations.
Pursuant to Rule 418 under the Securities Act of 1933, as amended (the &#147;Securities Act&#148;), the information contained in this letter is being provided to the Commission on a confidential supplemental basis only and is not to be filed with or
deemed part of the Registration Statement. The Company respectfully requests that the Staff return the unredacted version of this letter to it pursuant to Rule 418 of the Securities Act once the Staff has completed its review. We have provided a
self-addressed stamped envelope for this purpose. Kindly acknowledge receipt of this letter by stamping the enclosed copy of this letter and returning it in the envelope provided. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">*-*-*-* </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">If you have any questions or comments regarding the
foregoing, or if there is any additional information that we may provide to assist the Staff&#146;s review, please contact the undersigned at (617) <FONT STYLE="white-space:nowrap">570-1329.</FONT> </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="40%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>

<TD WIDTH="7%"></TD>

<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="92%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3">Sincerely,</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16" COLSPAN="3"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3">GOODWIN PROCTER LLP</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Gabriela Morales-Rivera</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Gabriela Morales-Rivera, Esq., <I>Goodwin Procter LLP </I></TD></TR>
</TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">cc:</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">E. Rand Sutherland, M.D., M.P.H., <I>Upstream Bio, Inc.</I> </P></TD></TR></TABLE>
<P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">Michael Paul Gray, M.B.A., <I>Upstream Bio, Inc.</I> </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">William D. Collins, Esq., <I>Goodwin Procter LLP</I> </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">Kathryn W. Clerici, Esq., <I>Goodwin Procter LLP</I> </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">Kristin VanderPas, Esq., <I>Cooley LLP</I> </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">Dave Peinsipp, Esq., <I>Cooley LLP</I> </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">Denny Won, Esq., <I>Cooley LLP</I> </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">Charles S. Kim, Esq., <I>Cooley LLP</I> </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">14 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FOIA CONFIDENTIAL TREATMENT REQUESTED BY UPSTREAM BIO, INC. </B></P>

</DIV></Center>

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