Under each of the legal entity’s equity plans, we recorded stock-based compensation in the following expense categories in our condensed consolidated statements of operations for employees and non-employees:


	Three Months Ended September 30, 2021						Nine Months Ended September 30, 2021
	BridgeBio Equity Plan		Other Subsidiaries Equity Plan		Total		BridgeBio Equity Plan		Other Subsidiaries Equity Plan		Total
	(in thousands)
Research and development	$	4,198	$	610	$	4,808	$	44,661	$	1,880	$	46,541
Selling, general and administrative		11,292		30		11,322		33,555		2,965		36,520
Total stock-based compensation	$	15,490	$	640	$	16,130	$	78,216	$	4,845	$	83,061


	Three Months Ended September 30, 2020								Nine Months Ended September 30, 2020
	BridgeBio Equity Plan		Eidos Equity Plan		Other Subsidiaries Equity Plan		Total		BridgeBio Equity Plan		Eidos Equity Plan		Other Subsidiaries Equity Plan		Total
	(in thousands)
Research and development	$	4,974	$	1,648	$	310	$	6,932	$	13,194	$	4,011	$	538	$	17,743
General and administrative		8,895		1,792		80		10,767		24,260		4,074		236		28,570
Total stock-based compensation	$	13,869	$	3,440	$	390	$	17,699	$	37,454	$	8,085	$	774	$	46,313

We have recorded $0.1 million and $3.3 million of stock-based compensation expense for the three and nine months ended September 30, 2021, respectively, for performance-based milestone awards that were achieved during the period and were settled in cash.

As of September 30, 2021, 7,977,872 shares and 8,938 shares were reserved for future issuances under our 2019 Amended and Restated Stock Option and Incentive Plan (the “2019 A&R Plan”) and the 2019 Inducement Equity Plan (the “2019 Inducement Plan”), respectively. Pursuant to the Merger Transactions, we also reserved 2,802,644 shares specifically under the Eidos Award Exchange (the “Eidos Award Exchange Plan”), all of which were issued upon execution of the Eidos Award Exchange as discussed below. The 2019 A&R Plan, the 2019 Inducement Plan and the Eidos Award Exchange Plan are collectively referred herein as the “Plans”.

On April 22, 2020, we completed our 2020 Stock and Equity Award Exchange Program (the “Exchange Program”) for certain subsidiaries, which was an opportunity for eligible controlled entities’ employees and consultants to exchange their subsidiary equity (including common stock, vested and unvested stock options and restricted stock awards (“RSAs”)) for BridgeBio equity (including common stock, vested and unvested stock options and RSAs) and/or performance-based milestone awards tied to the achievement of certain development and regulatory milestones. The Exchange Program aligns our incentive compensation structure for employees and consultants across the BridgeBio group of companies to be consistent with the achievement of our overall corporate goals. In connection with the Exchange Program, we issued awards of BridgeBio equity under the 2019 A&R Plan to 149 grantees covering 554,064 shares of common stock, 1,268,110 stock options to purchase common stock, 50,145 shares of RSAs and 22,611 shares of performance-based RSAs. The exchange also included performance-based milestone awards of up to $183.4 million to be settled in fully-vested RSAs in the future upon achievement of the milestones (collectively the “New Awards”). In consideration for all the subsidiaries’ shares tendered, BridgeBio increased its ownership in controlled entities included in the Exchange Program and the corresponding noncontrolling interest decreased.

On November 18, 2020, we completed a stock and equity award under our Exchange Program for a subsidiary. We issued awards of BridgeBio equity under the 2019 A&R Plan to 16 grantees covering 24,924 shares of common stock, 70,436 stock options to purchase common stock, and 10,772 shares of performance-based stock options to purchase common stock. The exchange also included performance-based milestone awards of up to $11.7 million to be settled in fully-vested RSAs in the future upon achievement of the milestones.

We considered the total shares of common stock and equity awards, whether vested or unvested, held by each participant in each controlled entity as the unit of account. The controlled entity’s common stock and equity awards in each unit of account was exchanged for a combination of BridgeBio’s common stock, time-based vesting equity awards and/or performance-based milestone awards. Other than the exchange of the controlled entity equity awards for performance-based milestone awards, all other exchanged BridgeBio equity awards retained the original vesting conditions. As a result, there was no incremental stock-based compensation expense resulting from the exchange of time-based equity awards.

At the completion of the Exchange Program, we determined $17.4 million of the performance-based milestone awards were probable of achievement and represented the incremental stock-based compensation cost resulting from the modification of time-based equity awards to performance-based milestone awards. These performance-based milestone awards were to be recognized over a period ranging from 0.7 year to 1.7 years. There was no incremental stock-based compensation cost arising from the completion of the Exchange Program on November 18, 2020. Under ASC 718, we account for such performance-based milestone awards as a liability in “Accrued compensation and benefits” and in “Other long-term liabilities” in the condensed consolidated balance sheets due to the fixed milestone amount that will be converted into a variable number of shares of BridgeBio common stock to be granted upon the achievement date.

During the nine months ended September 30, 2021, we recognized $25.8 million of stock-based compensation expense associated with milestone awards under the Exchange Program that were determined to be probable of achievement as of September 30, 2021. The related stock-based compensation expense for the three months ended September 30, 2021 was not material. Refer to Note 8 for contingent compensation accrued associated with performance-based milestones that are determined to be probable as of September 30, 2021.

Apart from the Exchange Program discussed above, we have performance-based milestone compensation arrangements with certain employees and consultants whose vesting is contingent upon meeting various regulatory and development milestones, with fixed monetary amounts known at inception that can be settled in the form of cash or equity at our sole discretion, upon achievement of each contingent milestone. Upon achievement of a contingent milestone and if such performance-based milestone awards are settled in the form of equity, these are satisfied in the form of fully-vested RSAs. We recognize such contingent stock-based compensation expense when the milestone is probable of achievement. For the three and nine months ended September 30, 2021, we recognized $0.7 million and $6.7 million, respectively, of stock-based compensation expense associated with performance-based milestone awards that were determined to be probable of achievement as of September 30, 2021. Refer to Note 8 for contingent compensation accrued associated with performance-based milestones awards that are determined to be probable as of September 30, 2021.

The following table summarizes BridgeBio’s stock option activity under the Plans for the nine months ended September 30, 2021:


	Options Outstanding					Weighted- Average Exercise Price per Option		Weighted- Average Remaining Contractual Life (years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2020				7,632,961
Regular equity program		6,778,112				$	23.83		8.8		320,473
Exchange Program		854,849				$	2.22		8.2		58,891
Granted				3,830,863
Regular equity program		1,054,191				$	63.82
Eidos Awards Exchange		2,776,672				$	16.33
Exercised				(1,069,978	)
Regular equity program		(292,143	)			$	19.93
Eidos Awards Exchange		(497,082	)			$	16.10
Exchange Program		(280,753	)			$	1.68
Cancelled				(222,579	)
Regular equity program		(105,089	)			$	27.41
Eidos Awards Exchange		(113,320	)			$	20.17
Exchange Program		(4,170	)			$	3.09
Outstanding as of September 30, 2021				10,171,267
Regular equity program		7,435,071				$	29.60		8.3	$	146,291
Eidos Awards Exchange		2,166,270				$	16.18		7.1	$	66,554
Exchange Program		569,926				$	2.48		7.4	$	25,299
Exercisable as of September 30, 2021				4,486,617
Regular equity program		2,889,270				$	23.73		8.0	$	68,522
Eidos Awards Exchange		1,102,497				$	12.22		6.2	$	38,200
Exchange Program		494,850				$	2.03		7.4	$	22,190

The options granted to employees and non-employees are exercisable at the price of BridgeBio’s common stock at the respective grant dates. The options granted have a service condition and generally vest over a period of four years.

The weighted-average grant date fair value of options granted during the nine months ended September 30, 2021 was $31.03.

The aggregate intrinsic value of options outstanding and exercisable as of September 30, 2021 in the table above are calculated based on the difference between the exercise price and the current fair value of BridgeBio common stock. The total intrinsic value of options exercised during the nine months ended September 30, 2021 was $50.4 million.

During the three and nine months ended September 30, 2021, we recognized stock-based compensation expense of $8.1 million and $21.9 million, respectively, related to stock options under the Plans. As of September 30, 2021, there was $71.6 million of total unrecognized compensation cost related to stock options under the Plans that is expected to be recognized over a weighted-average period of 2.1 years.

During the three and nine months ended September 30, 2021, we recognized stock-based compensation expense of $6.4 million and $16.8 million, respectively, related to RSUs under the Plans. As of September 30, 2021, there was $80.0 million of total unrecognized compensation cost related to RSUs under the Plans that is expected to be recognized over a weighted-average period of 3.1 years.

As of September 30, 2021, there was $11.7 million of total unrecognized compensation cost related to RSAs under the Plans that is expected to be recognized over a weighted-average period of 2.1 years. The respective balances of unvested RSAs as of September 30, 2021 and December 31, 2020 are included as outstanding shares disclosed in the condensed consolidated balance sheets as the shares were issued but are subject to forfeiture per the terms of the awards.

During the three and nine months ended September 30, 2021, stock-based compensation expense related to our ESPP was immaterial. As of September 30, 2021, 4,235,440 shares were reserved for future issuance under the ESPP.

Prior to the Merger Transactions, Eidos issued its own equity-based awards under the Eidos 2016 Equity Incentive Plan and the Eidos 2018 Stock Option and Incentive Plan (collectively, the “Eidos Plans”). Upon closing of the Merger Transactions, we issued 2,776,672 stock options to purchase common stock of BridgeBio and 25,972 shares of BridgeBio RSUs to 88 employees of Eidos under the Eidos Award Exchange in exchange for their then outstanding common stock options and RSUs under the Eidos Plans (the “Replaced Awards”). The awards issued in the Eidos Award Exchange have the same vesting terms and conditions as the Replaced Awards. We evaluated the exchange of the awards as a modification under ASC 718 and recognized no incremental compensation cost from such modification.

Stock-based compensation under the Eidos Plans from January 1, 2021 until the closing of the Merger Transactions was immaterial.