|
CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)
In Thousands, unless otherwise specified
|
12 Months Ended |
|
Dec. 31, 2014
|
Dec. 31, 2013
|
Dec. 31, 2012
|
| Net Cash Provided by (Used in) Operating Activities [Abstract] |
|
|
|
| Net loss |
$ (53,365) |
$ (41,202) |
$ (31,984) |
| Adjustments to reconcile net loss to net cash used in operating activities: |
|
|
|
| Depreciation and amortization |
427 |
236 |
207 |
| Stock-based compensation expense |
12,360 |
9,676 |
7,400 |
| Amortization of premiums and discounts on available-for-sale marketable securities |
290 |
|
|
| Non-cash expense related to purchase of technology rights |
1,197 |
|
|
| Non-cash expense related to acquisition of license |
|
|
1,957 |
| Change in fair value of obligation to issue a warrant |
|
|
431 |
| Loss on disposal of fixed assets |
4 |
|
|
| Changing in operating assets and liabilities: |
|
|
|
| Prepaid expenses and other current assets |
27 |
(382) |
(376) |
| Accounts payable |
287 |
912 |
(425) |
| Accrued expenses and other liabilities |
2,119 |
3,738 |
189 |
| Liability classified stock-based compensation awards |
(248) |
717 |
|
| Net cash used in operating activities |
(36,902) |
(26,305) |
(22,601) |
| Investing activities |
|
|
|
| Purchases of property and equipment |
(2,429) |
(56) |
(310) |
| Purchases of investments |
(39,361) |
(118,190) |
(154,028) |
| Maturities of investments |
85,047 |
94,853 |
108,479 |
| Increase in restricted cash |
(117) |
|
|
| Net cash (used in) provided by investing activities |
43,140 |
(23,393) |
(45,859) |
| Financing activities |
|
|
|
| Proceeds from the exercise of stock options |
20 |
33 |
3 |
| Net proceeds from the issuance of common stock and restricted common stock |
9,534 |
59,760 |
57,599 |
| Cash used to settle restricted stock liability |
(780) |
(1,302) |
|
| Net cash provided by financing activities |
8,774 |
58,491 |
57,602 |
| (Decrease) increase in cash and cash equivalents |
15,012 |
8,793 |
(10,858) |
| Cash and cash equivalents at beginning of period |
18,889 |
10,096 |
20,954 |
| Cash and cash equivalents at end of period |
33,901 |
18,889 |
10,096 |
| Supplemental disclosure of non-cash investing and financing activities |
|
|
|
| Accretion of redeemable convertible preferred stock to redemption value |
|
|
6 |
| Conversion of redeemable convertible preferred stock upon initial public offering |
|
|
68,147 |
| Reclassification of obligation to issue warrant from liabilities to equity |
|
|
837 |
| Proceeds from the issuance of common stock included in prepaid expenses and other current assets |
2,085 |
|
|
| Purchase of property and equipment in accounts payable |
$ 196 |
|
|