4.	Balance Sheet Details

Short-Term

Investments

The following is a summary of

our short-term investments (in thousands):

	December 31, 201 7
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. corporate debt securities	$	13,003	$	—	$	(10	)	$	12,993
U.S. commercial paper		4,929		—		—			4,929
Foreign commercial paper		9,874		—		—			9,874
Total	$	27,806	$	—	$	(10	)	$	27,796

	December 31, 201 6
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. corporate debt securities	$	12,048	$	—	$	(9	)	$	12,039
Foreign corporate debt		14,065		—		(8	)		14,057
U.S. commercial paper		8,635		—		—			8,635
Foreign commercial paper		2,993		—		—			2,993
Total	$	37,741	$	—	$	(17	)	$	37,724

The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity.

We regularly monitor and evaluate the realizable value of our marketable securities. We did

not

recognize any impairment losses for the years ended

December 31, 2017

and

2016.

Inventory

Inventory consists of the following (in thousands):

	December 31,
	2017		2016
Raw materials	$	2,754	$	1,647
Work in process		4,166		1,104
Finished goods		3,188		2,589
Total inventory	$	10,108	$	5,340

As of

December 31, 2017,

total inventory include

$7.1

million related to SUSTOL and

$3.0

million related to CINVANTI. As of

December 31, 2016,

total inventory included

$5.3

million related to SUSTOL.

Property and Equipment

Property and equipment

, net consists of the following (in thousands):

	December 31,
	2017			2016
Scientific equipment	$	9,742		$	7,952
Leasehold improvements		1,654			1,635
Computer equipment and software		1,420			1,429
Furniture, fixtures and office equipment		1,024			674
Property and equipment , gross		13,840			11,690
Less: accumulated depreciation and amortization		(7,859	)		(6,614	)
Property and equipment, net	$	5,981		$	5,076

Depreciation and amortization expense for the years ended

December

31,

2017,

2016

and

2015

was

$1.5

million,

$1.1

million and

$0.7

million, respectively. As of

December 31, 2017

and

2016,

$2.0

million and

$1.7

million of property and equipment, respectively, was in process and

not

depreciated during the respective years.

Accrued Payroll and Employee Liabilities and Other Accrued

Liabilities

Accrued payroll and employee liabilities

consist of the following (in thousands):

	December 31,
	20 17		2016
Accrued employee salaries and benefits	$	2,730	$	2,236
Accrued bonuses		5,044		3,474
Accrued expenses for realignment (see Note 6)		1,086		2,704
Total accrued payroll and employee liabilities	$	8,860	$	8,414

Other accrued

liabilities consist of the following (in thousands):

	December 31,
	2017		2016
Accrued consulting and professional fees	$	6,869	$	4,703
Accrued accounts payable		148		1,039
Accrued product sales allowances		9,319		342
Deferred rent		651		116
Other accrued liabilities		188		88
Total other accrued liabilities	$	17,175	$	6,288