<PAGE>
                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549

                                 SCHEDULE 13D

                 UNDER THE SECURITIES EXCHANGE ACT OF 1934

           --------------------------------------------------------
                            ADVANCED MAGNETICS, INC.
           --------------------------------------------------------
                                (Name of Issuer)

                                  Common Stock
           --------------------------------------------------------
                          (Title of Class of Securities)

                                  00753P 10 3
           --------------------------------------------------------
                                 (CUSIP Number)

                                   Hope Flack
                                    BVF Inc.
                     c/o Grosvenor Capital Management, L.P.
                        333 West Wacker Drive, Suite 1600
                             Chicago, Illinois 60606
                                  (312) 263-7777
           --------------------------------------------------------
                (Name, Address and Telephone Number of Person 
               Authorized to Receive Notices and Communications)

                               OCTOBER 18, 1996
           --------------------------------------------------------
            (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 which is the subject of this Schedule 13D, and is 
filing this schedule because of Rule 13d-1(b)(3) or (4), check the following 
box / /.

   Check the following box if a fee is being paid with this statement / /. 
(A fee is not required only if the reporting person: (1) has a previous 
statement on file reporting beneficial ownership of more than five percent of 
the class of securities described in Item 1; and (2) has filed no amendment 
subsequent thereto reporting beneficial ownership of five percent or less of 
such class. (See Rule 13d-7.)

   NOTE:  Six copies of this statement, including all exhibits, should be 
filed with the Commission. SEE Rule 13d-1(a) for other parties to whom copies 
are to be sent.

                        (Continued on following pages)

                              (Page 1 of 7 Pages)

- ------------------------

(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 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).


<PAGE>

CUSIP No. 00753P 10 3               SCHEDULE 13D              PAGE  2 OF 7 PAGES
          -----------                                               -    -


- -------------------------------------------------------------------------------
 (1) NAME OF REPORTING PERSON.
     S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

        Biotechnology Value Fund, L.P.
- -------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER     (a)  /X/
     OF A GROUP*                               (b)  / /
- -------------------------------------------------------------------------------
 (3) SEC USE ONLY

- -------------------------------------------------------------------------------
 (4) SOURCE OF FUNDS*
     WC
- -------------------------------------------------------------------------------
 (5) CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
     ITEMS 2(d) or 2(e)                             / /
- -------------------------------------------------------------------------------
 (6) CITIZENSHIP OR PLACE OF ORGANIZATION
     Delaware
- -------------------------------------------------------------------------------
NUMBER OF SHARES              (7) SOLE VOTING POWER
 BENEFICIALLY OWNED               -0-
 BY EACH REPORTING           --------------------------------------------------
 PERSON WITH                  (8) SHARED VOTING POWER
                                  194,820
                             --------------------------------------------------
                              (9) SOLE DISPOSITIVE POWER
                                  -0-
                             --------------------------------------------------
                             (10) SHARED DISPOSITIVE POWER
                                  194,820
- -------------------------------------------------------------------------------
(11) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
     194,820
- -------------------------------------------------------------------------------
(12) CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
                                                    / /
- -------------------------------------------------------------------------------
(13) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
     2.88%
- -------------------------------------------------------------------------------
(14) TYPE OF REPORTING PERSON
     PN
- -------------------------------------------------------------------------------


<PAGE>

CUSIP No. 00753P 10 3               SCHEDULE 13D              PAGE  3 OF 7 PAGES
          -----------                                               -    -


- -------------------------------------------------------------------------------
 (1) NAME OF REPORTING PERSON.
     S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

        BVF Partners L.P.
- -------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER     (a)  /X/
     OF A GROUP*                               (b)  / /
- -------------------------------------------------------------------------------
 (3) SEC USE ONLY

- -------------------------------------------------------------------------------
 (4) SOURCE OF FUNDS*
     00
- -------------------------------------------------------------------------------
 (5) CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
     ITEMS 2(d) or 2(e)                             / /
- -------------------------------------------------------------------------------
 (6) CITIZENSHIP OR PLACE OF ORGANIZATION
     Delaware
- -------------------------------------------------------------------------------
NUMBER OF SHARES              (7) SOLE VOTING POWER
 BENEFICIALLY OWNED               -0-
 BY EACH REPORTING           --------------------------------------------------
 PERSON WITH                  (8) SHARED VOTING POWER
                                  393,400
                             --------------------------------------------------
                              (9) SOLE DISPOSITIVE POWER
                                  -0-
                             --------------------------------------------------
                             (10) SHARED DISPOSITIVE POWER
                                  393,400
- -------------------------------------------------------------------------------
(11) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
     393,400
- -------------------------------------------------------------------------------
(12) CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
                                                    / /
- -------------------------------------------------------------------------------
(13) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
     5.81%
- -------------------------------------------------------------------------------
(14) TYPE OF REPORTING PERSON
     PN
- -------------------------------------------------------------------------------

<PAGE>

CUSIP No. 00753P 10 3               SCHEDULE 13D              PAGE  4 OF 7 PAGES
          -----------                                               -    -


- -------------------------------------------------------------------------------
 (1) NAME OF REPORTING PERSON.
     S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

        BVF Inc.
- -------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER     (a)  /X/
     OF A GROUP*                               (b)  / /
- -------------------------------------------------------------------------------
 (3) SEC USE ONLY

- -------------------------------------------------------------------------------
 (4) SOURCE OF FUNDS*
     WC, 00
- -------------------------------------------------------------------------------
 (5) CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
     ITEMS 2(d) or 2(e)                             / /
- -------------------------------------------------------------------------------
 (6) CITIZENSHIP OR PLACE OF ORGANIZATION
     Delaware
- -------------------------------------------------------------------------------
NUMBER OF SHARES              (7) SOLE VOTING POWER
 BENEFICIALLY OWNED               -0-
 BY EACH REPORTING           --------------------------------------------------
 PERSON WITH                  (8) SHARED VOTING POWER
                                  393,400
                             --------------------------------------------------
                              (9) SOLE DISPOSITIVE POWER
                                  -0-
                             --------------------------------------------------
                             (10) SHARED DISPOSITIVE POWER
                                  393,400
- -------------------------------------------------------------------------------
(11) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
     393,400
- -------------------------------------------------------------------------------
(12) CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES
                                                    / /
- -------------------------------------------------------------------------------
(13) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
     5.81%
- -------------------------------------------------------------------------------
(14) TYPE OF REPORTING PERSON
     IA, CO
- -------------------------------------------------------------------------------


<PAGE>

CUSIP No. 00753P 10 3               SCHEDULE 13D              PAGE  5 OF 7 PAGES
          -----------                                               -    -


ITEM 1.  SECURITY AND ISSUER.

    This statement on Schedule 13D (this "Statement") relates to the Common 
Stock, par value $0.10 per share (the "Stock"), of ADVANCED MAGNETICS, INC.
("Advanced Magnetics"). The principal executive office of Advanced Magnetics 
is located at 725 Concord Avenue, Cambridge, MA 02138.

ITEM 2.  IDENTITY AND BACKGROUND.

    The persons filing this Statement, the persons enumerated in Instruction C
of Schedule 13D and, where applicable, their respective places of organization,
general partners, directors, executive officers and controlling persons, and
certain information regarding each of them, are as follows:

    (a) Biotechnology Value Fund, L.P., a Delaware limited partnership ("BVF, 
L.P."), BVF Partners L.P., a Delaware limited partnership ("Partners"), BVF 
Inc., a Delaware corporation ("BVF Inc."), and Mark N. Lampert, an individual 
("Lampert").

    (b) The business address of BVF, L.P. and Partners is 333 West Wacker 
Drive, Suite 1600, Chicago, Illinois 60606. The business address of BVF Inc. 
and Lampert is One Sansome Street, 39th Floor, San Francisco, California 94104.

    (c) Partners is the general partner of BVF, L.P., which is an investment 
limited partnership. BVF Inc. is an investment adviser to and general partner 
of Partners. Lampert is the sole shareholder and director and the President 
and Secretary of BVF Inc.

    (d) During the last five years, none of such persons has been convicted 
in a criminal proceeding (excluding traffic violations and similar 
misdemeanors).

    (e) During the last five years, none of such persons was a 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) Lampert is a citizen of the United States of America.

ITEM 3.  SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

    Neither BVF, L.P., Partners nor BVF Inc. (collectively, the "Reporting 
Persons") has purchased any shares of the Stock since the last filing in 
respect of this Statement. In the past, Partners in its capacity as general 
partner of BVF, L.P., has purchased on behalf of such limited partnership 
shares of the Stock utilizing funds provided by BVF, L.P. from its working 
capital pursuant to the terms of its limited partnership agreement with 
Partners. Partners, in its capacity as investment manager with respect to a 
managed accounts, has purchased on behalf of such managed account shares of 
the Stock utilizing funds under management by Partners pursuant to an 
investment management agreement between Partners and


<PAGE>

CUSIP No. 00753P 10 3               SCHEDULE 13D              PAGE  6 OF 7 PAGES
          -----------                                               -    -


such managed account. In addition, BVF Inc., in its capacity as investment 
manager with respect to certain managed accounts, has purchased on behalf of 
such managed accounts shares of the Stock utilizing funds under management 
(including funds invested by BVF Inc. on its own behalf) by BVF Inc. pursuant 
to investment management agreements between BVF Inc. and such managed 
accounts or the operating agreements of such managed accounts.


ITEM 4.  PURPOSE OF TRANSACTION.

    The sole purpose of the acquisitions and dispositions of the Stock 
reported in this Statement and the amendments hereto was and is for 
investment. The Reporting Persons did not at the time of such acquisitions 
and dispositions of the Stock, and do not presently, have any plan to acquire 
control of Advanced Magnetics. The Reporting Persons may acquire or dispose 
of additional shares of the Stock from time to time.


ITEM 5.  INTEREST IN SECURITIES OF THE ISSUER.

    (a) BVF, L.P. beneficially owns 194,820 shares of the Stock, and Partners 
and BVF Inc., each beneficially owns 393,400 shares of the Stock, 
approximately 2.88% and 5.81%, respectively, of the aggregate number of 
shares outstanding as of June 30, 1996.

    (b) BVF, L.P. shares voting and dispositive power over the 194,820 shares 
of the Stock it beneficially owns with Partners. Partners and BVF Inc. share 
voting and dispositive power over the 393,400 shares of the Stock it 
beneficially owns with BVF, L.P. and the managed accounts on whose behalf 
Partners, as investment manager, purchased such shares. The managed account 
on whose behalf Partners has purchased shares of the Stock are Investment 10 
L.L.C., an Illinois limited liability company ("I10"), Palmundo L.D.C., a 
limited duration company organized under the laws of the Cayman Islands 
("Palmundo"), Z.P.G. Securities, L.L.C., a New York limited liability company 
("ZPG") and Biotechnology Value Fund, Ltd. a Cayman Islands Corporation ("BVF 
Ltd."). I10, Palmundo, ZPG and BVF Ltd. are collectively referred to herein 
as the "Accounts." The Accounts specialize in holding biotechnology stocks 
for investment purposes and the business address of each is c/o Grosvenor 
Capital Management, L.P., 333 West Wacker Drive, Suite 1600, Chicago, 
Illinois 60606.

    (c) Exhibit B hereto contains information as to all transactions in the 
Stock by the Reporting Persons during the past 60 days. All such transactions 
were made for cash and involved the resale by the Reporting Persons of 
restricted securities in accordance with exemptions under applicable federal 
and state securities laws. No other transactions in the Stock have been 
effected by the Reporting Persons since March 15, 1996.

    (d) BVF, L.P. and the Accounts are entitled to receive dividends and any 
sale proceeds with respect to the Stock in proportion to their respective 
ownership interests therein.

    (e) N/A


<PAGE>

CUSIP No. 00753P 10 3               SCHEDULE 13D              PAGE  7 OF 7 PAGES
          -----------                                               -    -


ITEM 6.  CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
  TO SECURITIES OF THE ISSUER.

    Partners is the general partner of BVF, L.P. pursuant to a limited 
partnership agreement which authorizes Partners, among other things, to 
invest the funds of BVF, L.P. in the Stock and to vote and dispose of the 
Stock. Pursuant to such limited partnership agreement, Partners is entitled 
to allocations based on assets under management and realized and unrealized 
gains thereon. Pursuant to investment management agreements with the Accounts, 
Partners has the authority, among other things, to invest funds of the Accounts 
in the Stock and to vote and dispose of the Stock. Pursuant to such agreements, 
Partners receives fees based on assets under management and realized and 
unrealized gains thereon. BVF Inc. is the general partner of Partners and may 
be deemed to own beneficially securities over which Partners exercises voting 
and dispositive power.

ITEM 7.  MATERIAL TO BE FILED AS EXHIBITS

    Exhibit A - Agreement Regarding Joint Filing

    Exhibit B - Transactions in the Stock by the Reporting Persons during the 
last 60 days

    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.

Dated: October 29, 1996

                                    BIOTECHNOLOGY VALUE FUND, L.P.

                                    By: BVF Partners, L.P., its general partner

                                        By: BVF Inc., its general partner

                                            By: /s/ MARK N. LAMPERT
                                                --------------------------------
                                                Mark N. Lampert, President

                                    BVF PARTNERS L.P.

                                        By: BVF Inc., its general partner

                                            By: /s/ MARK N. LAMPERT
                                                --------------------------------
                                                Mark N. Lampert, President

                                    BVF INC.

                                            By: /s/ MARK N. LAMPERT
                                                --------------------------------
                                                Mark N. Lampert, President









<PAGE>
                                       
                                                                     EXHIBIT A
                        AGREEMENT REGARDING JOINT FILING

     The undersigned, Biotechnology Value Fund, L.P., a Delaware limited 
partnership, BVF Inc., a Delaware Corporation, and BVF Partners L.P., 
a Delaware limited partnership, hereby agree and acknowledge that the 
amended statement containing the information required by Schedule 13D, 
to which this Agreement is attached as an exhibit, is filed on behalf of 
each of them. The undersigned further agree that any amendments or supplements 
thereto shall also be filed on behalf of each of them.

     Dated: October 29, 1996
                                     
                                     BIOTECHNOLOGY VALUE FUND, L.P.

                                     By: BVF Partners L.P., its general partner

                                         By: BVF Inc., its general partner

                                              By: /s/ MARK N. LAMPERT
                                                 ------------------------------
                                                 Mark N. Lampert, President


                                         BVF PARTNERS L.P.

                                         By: BVF Inc., its general partner

                                              By: /s/ MARK N. LAMPERT
                                                 ------------------------------
                                                 Mark N. Lampert, President

                                         BVF INC.

                                         By: /s/ MARK N. LAMPERT
                                             ------------------------------
                                             Mark N. Lampert, President







<PAGE>
                                       
                                                                  EXHIBIT B

                           TRANSACTIONS IN THE STOCK
                BY THE REPORTING PERSONS DURING THE LAST 60 DAYS

   SETTLEMENT                    FOR THE                 PRICE      TYPE OF
     DATE(1)            BY      ACCOUNT OF   QUANTITY   PER SHARE    TRADE
- -----------------    --------   ----------   ---------   --------   --------
September 6, 1996    Partners   BVF Ltd.       2,000     $18.2917   Purchase
September 6, 1996    Partners   BVF, L.P.      4,000     $18.2917   Purchase
September 6, 1996    Partners   I10            3,000     $18.2917   Purchase
September 9, 1996    Partners   BVF Ltd.       3,700     $18.25     Purchase
September 20, 1996   Partners   BVF Ltd.       5,000     $17.25     Purchase
September 23, 1996   Partners   ZPG            3,000     $16.875    Sale
September 23, 1996   Partners   Palmundo       3,600     $16.875    Sale
October 9, 1996      Partners   ZPG           12,000     $17.0625   Sale(2)
October 9, 1996      Partners   Palmundo      10,000     $17.0625   Sale(2)
October 9, 1996      Partners   BVF Ltd.      22,000     $17.0781   Purchase(2)
October 18, 1996     Partners   BVF Ltd.       6,500     $15.4554   Purchase(3)
October 30, 1996     Partners   BVF Ltd.      21,200     $15.00     Purchase
October 31, 1996     Partners   BVF Ltd.      15,000     $15.00     Purchase
October 31, 1996     Partners   BVF L.P.      10,000     $15.00     Purchase
October 31, 1996     Partners   I10            2,800     $15.00     Purchase

- -------------------
(1) All trades through Daiken Securities except (2) through Mr. Stock 
    and (3) through Preferred Technology, Inc.