UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

(Rule 13d-101)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO § 240.13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO

§ 240.13d-2(a)

(Amendment No. 1)¹

Five Prime Therapeutics, Inc.

(Name of Issuer)

Common Stock, par value $0.001

(Title of Class of Securities)

33830X104

(CUSIP Number)

JAMES KRATKY

BVF Partners L.P.

44 Montgomery St., 40th Floor

San Francisco, California 94104

(415) 525-8890

ADAM W. FINERMAN, ESQ.

OLSHAN FROME WOLOSKY LLP

1325 Avenue of the Americas

New York, New York 10019

(212) 451-2300

(Name, Address and Telephone Number of Person

Authorized to Receive Notices and Communications)

October 6, 2020

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box ☒.

Note:  Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits.  See § 240.13d-7 for other parties to whom copies are to be sent.

1              The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

The following constitutes Amendment No. 1 to the Schedule 13D filed by the undersigned (“Amendment No. 1”). This Amendment No. 1 amends the Schedule 13D as specifically set forth herein.

Item 2 is hereby amended and restated to read as follows:

(a)       This statement is filed by:

Each of the foregoing is referred to as a “Reporting Person” and collectively as the “Reporting Persons.” Each of the Reporting Persons is party to that certain Joint Filing Agreement, as further described in Item 6. Accordingly, the Reporting Persons are hereby filing a joint Schedule 13D.

(b)       The business address of BVF, BVF GP, BVF2, BVF2 GP, BVF GPH, Partners, BVF Inc. and Mr. Lampert is 44 Montgomery St., 40^th Floor, San Francisco, California 94104. The business address of Trading Fund OS and Partners OS is PO Box 309 Ugland House, Grand Cayman, KY1-1104, Cayman Islands.

(c)       The principal business of each of BVF, BVF2, and Trading Fund OS is investing in securities. The principal business of BVF GP, BVF2 GP, and Partners OS is serving as the general partner of BVF, BVF2, and Trading Fund OS, respectively. The principal business of BVF GPH is serving as the sole member of each of BVF GP and BVF2 GP. The principal business of Partners is serving as the investment manager of each of BVF, BVF2, Trading Fund OS and the Partners Managed Accounts, and the sole member of Partners OS. The principal business of BVF Inc. is serving as the general partner of Partners and the managing member of BVF GPH. Mr. Lampert is serving as the sole officer and director of BVF Inc.

(d)       No Reporting Person has, during the last five years, been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).

(e)       No Reporting Person has, during the last five years, been party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

(f)       Mr. Lampert is a citizen of the United States of America.

Item 3 is hereby amended and restated to read as follows:

The Shares purchased by BVF, BVF2 and Trading Fund OS were purchased with working capital (which may, at any given time, include margin loans made by brokerage firms in the ordinary course of business) in open market purchases, except as otherwise noted. The aggregate purchase price of the 4,336,875 Shares beneficially owned by BVF is approximately $30,559,018, including brokerage commissions. The aggregate purchase price of the 3,281,151 Shares beneficially owned by BVF2 is approximately $24,122,736, including brokerage commissions. The aggregate purchase price of the 566,223 Shares beneficially owned by Trading Fund OS is approximately $4,240,762, including brokerage commissions. The aggregate purchase price of the 180,104 Shares held in the Partners Managed Accounts is approximately $695,218, including brokerage commissions.

Item 5 is hereby amended and restated to read as follows:

(a)       The aggregate percentage of Shares reported owned by each person named herein is based on 36,627,925 Shares outstanding as of July 31, 2020, as disclosed in the Issuer’s Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on August 6, 2020.

As of the close of business on October 8, 2020, (i) BVF beneficially owned 4,336,875 Shares, representing percentage ownership of approximately 11.8% of the Shares outstanding, (ii) BVF2 beneficially owned 3,281,151 Shares, representing percentage ownership of approximately 9.0% of the Shares outstanding, (iii) Trading Fund OS beneficially owned 566,223 Shares, representing percentage ownership of approximately 1.6% of the Shares outstanding, and (iv) 180,104 Shares were held in the Partners Managed Accounts, representing percentage ownership of less than 1% of the Shares outstanding.

BVF GP, as the general partner of BVF, may be deemed to beneficially own the 4,336,875 shares of Common Stock beneficially owned by BVF, representing percentage ownership of approximately 11.8% of the shares of Common Stock outstanding.

BVF2 GP, as the general partner of BVF2, may be deemed to beneficially own the 3,281,151 shares of Common Stock beneficially owned by BVF2, representing percentage ownership of approximately 9.0% of the shares of Common Stock outstanding.

Partners OS, as the general partner of Trading Fund OS, may be deemed to beneficially own the 566,223 Shares beneficially owned by Trading Fund OS, representing percentage ownership of approximately 1.6% of the Shares outstanding.

BVF GPH, as the sole member of each of BVF GP and BVF2 GP, may be deemed to beneficially own the 7,618,026 shares of Common Stock beneficially owned in the aggregate by BVF and BVF2, representing percentage ownership of approximately 20.8% of the shares of Common Stock outstanding.

Partners, as the general partner of BVF and BVF2, the sole member of Partners OS, and the investment manager of Trading Fund OS and the Partners Managed Account, may be deemed to beneficially own the 8,364,353 Shares beneficially owned in the aggregate by BVF, BVF2, Trading Fund OS, and the Partners Managed Accounts, representing percentage ownership of approximately 22.8% of the Shares outstanding.

BVF Inc., as the general partner of Partners, may be deemed to beneficially own the 8,364,353 Shares beneficially owned by Partners, representing percentage ownership of approximately 22.8% of the Shares outstanding.

Mr. Lampert, as a director and officer of BVF Inc. may be deemed to beneficially own the 8,364,353 Shares beneficially owned by BVF Inc., representing percentage ownership of approximately 22.8% of the Shares outstanding.

(b)       Each of BVF, BVF2 and Trading Fund OS shares with Partners voting and dispositive power over the Shares each such entity beneficially owns. BVF shares with BVF GP voting and dispositive power over the Shares beneficially owned by BVF. BVF2 shares with BVF2 GP voting and dispositive power over the Shares beneficially owned by BVF2. Each of BVF GP and BVF2 GP shares with BVF GPH voting and dispositive power over the Shares each such entity beneficially owns. Trading Fund OS shares with Partners OS voting and dispositive power over the Shares beneficially owned by Trading Fund OS. Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the 8,364,353 Shares they may be deemed to beneficially own with BVF, BVF GP, BVF2, BVF2 GP, Trading Fund OS, Partners OS, BVF GPH and the Partners Managed Accounts.

(c)       Schedule A annexed hereto lists all transactions in securities of the Issuer during the past sixty days by the Reporting Persons. All of such transactions were effected in the open market, except as otherwise noted.

(d)       No person other than the Reporting Persons is known to have the right to receive, or the power to direct the receipt of dividends from, or proceeds from the sale of, the Shares.

(e)       Not applicable.

Item 7 is hereby amended to add the following exhibit:

SIGNATURES

After reasonable inquiry and to the best of his knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: October 8, 2020

BIOTECHNOLOGY VALUE FUND, L.P.

BIOTECHNOLOGY VALUE FUND II, L.P.

Biotechnology Value Trading Fund OS LP

BVF Partners L.P.

(Through the BVF Partners L.P. Managed Account)