SCHEDULE 13G

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Date of Event which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

x Rule 13d-1(b)

¨ Rule 13d-1(c)

¨ Rule 13d-1(d)

*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 (the “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).

CUSIP No.  503459604

CUSIP No.  503459604

CUSIP No.  503459604

CUSIP No.  503459604

Amendment No. 1 to Schedule 13G

This Amendment No. 1 to Schedule 13G amends and supplements the previously filed Schedules 13G filed by Baker Bros. Advisors LP (the “Adviser”), Baker Bros. Advisors (GP) LLC (the “Adviser GP”), Julian C. Baker and Felix J. Baker. Except as supplemented herein, such statements, as heretofore amended and supplemented, remain in full force and effect. 

This Schedule 13G is being filed jointly by the Adviser, Adviser GP, Felix J. Baker and Julian C. Baker (collectively, the “Reporting Persons”).

(a) ¨ Broker or dealer registered under Section 15 of the Exchange Act.

(b) ¨ Bank as defined in section 3(a)(6) of the Exchange Act.

(c) ¨ Insurance company as defined in section 3(a)(19) of the Exchange Act.

(d) ¨ Investment company registered under section 8 of the Investment Company Act of 1940.

(e) x An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E).

(f) ¨ An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F).

(g) x A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G).

(h) ¨ A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act.

(i) ¨ A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940.

(j) ¨ Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

Items 5 through 9 and 11 of each of the cover pages to this Schedule 13G are incorporated herein reference. Set forth below is the aggregate number of shares of Common Stock the Issuer as well as shares of Common Stock that may be acquired upon conversion of the Series F Convertible Preferred Stock (“Series F Preferred”) convertible into Common Stock of the Issuer a rate of 285.5 shares of Common Stock for each share of Series F Preferred, directly held by each of Baker Brothers Life Sciences, L.P. (“Life Sciences”), 14159, L.P. (“14159”), and 667, L.P. (“667”, and together with Life Sciences and 14159, the “Funds”) subject to the limitation on conversion described below. The information set forth below is based upon 15,225,980 shares of Common Stock outstanding as of November 7, 2014, as reported on the Issuer’s Form 10-Q filed with the SEC on November 12, 2014. Such percentage figures are calculated in accordance with Rule 13d-3 under the Securities Exchange Act of 1934, as amended.

The Series F Preferred is only exercisable to the extent that the holders thereof together with their affiliates would beneficially own, for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, no more than 9.999% of the outstanding shares of Common Stock of the Issuer after conversion (“Beneficial Ownership Limitation”). As a result of this restriction, the number of shares that may be issued upon conversion of the Series F Preferred by the above holders may change depending upon changes in the outstanding shares. The number of shares of Common Stock issuable upon conversion of the Series F Preferred held by any Reporting Person affiliate will also depend upon the extent to which the Series F Preferred held by other affiliates have theretofore been converted.

Pursuant to the amended and restated management agreements among the Adviser, the Funds and their respective general partners, the Adviser has complete and unlimited discretion and authority with respect to the Funds’ investments and voting power over investments.

The Adviser GP, Felix J. Baker and Julian C. Baker as principals of the Adviser GP, and the Adviser may be deemed to be beneficial owners of securities of the Issuer directly held by the Funds, and may be deemed to have the power to vote or direct the vote of and the power to dispose or direct the disposition of such securities.

The Reporting Persons disclaim beneficial ownership of the securities held by each of the Funds, and this Schedule 13G shall not be deemed an admission that the Reporting Persons are the beneficial owners of such securities for purposes of Section 13(d) or for any other purpose.

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

February 17, 2015