UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                 Schedule 13G/A

                    Under the Securities Exchange Act of 1934

                        Interneuron Pharmaceuticals, Inc.

                     Common Stock, $.001 par value per share
                     ---------------------------------------
                         (Title of Class of Securities)

                                February 10, 2001

                            (CUSIP Number: 460573108)

                                December 31, 2000
                                -----------------
                       Date of event which requires filing

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

                                |_| Rule 13d-1(b)
                                |X| 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 in the remainder of this cover page shall not be deemed
to be filled 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
to Schedule 13G).


- --------------------------------------------------------------------------------
CUSIP No. 460573108                                       13G
- --------------------------------------------------------------------------------
    1     NAMES OF REPORTING PERSONS
          S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

          Lindsay A. Rosenwald, M.D.
- --------------------------------------------------------------------------------
    2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                      (a)
                                                                      (b)
- --------------------------------------------------------------------------------
    3     SEC USE ONLY

- --------------------------------------------------------------------------------
    4     CITIZENSHIP OR PLACE OF ORGANIZATION
          United States

- --------------------------------------------------------------------------------
 NUMBER OF SHARES          5   SOLE VOTING POWER
BENEFICIALLY OWNED BY
EACH REPORTING PERSON          2,641,649
       WITH              -------------------------------------------------------
                           6   SHARED VOTING POWER
                               None
                         -------------------------------------------------------
                           7   SOLE DISPOSITIVE POWER
                               2,641,649
                         -------------------------------------------------------
                           8   SHARED DISPOSITIVE POWER
                               None
- --------------------------------------------------------------------------------
    9     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          2,641,649
- --------------------------------------------------------------------------------
   10     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES*

- --------------------------------------------------------------------------------
   11     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
           5.8%

- --------------------------------------------------------------------------------
   12     TYPE OF REPORTING PERSON*

          IN
- --------------------------------------------------------------------------------


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ITEM 1(a). NAME OF ISSUER:

            Interneuron Pharmaceuticals, Inc..

ITEM 1(b). ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES:

            One Ledgemount Center
            99 Hayden Avenue
            Lexington, MA 02421

            ITEM 2(a) NAME OF PERSON FILING: Lindsay A. Rosenwald, M.D.

ITEM 2(b) ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE:

            Dr. Rosenwald's business address is 787 Seventh Avenue, 48th Floor,
            New York, New York, 10019.

ITEM 2(c). CITIZENSHIP:

            Dr. Rosenwald is a citizen of the United States of America.

ITEM 2(d). TITLE OF CLASS OF SECURITIES:

            Common Stock, par value $.001 per share.

ITEM 2(e). CUSIP NUMBER: 460573108

ITEM 3. |X| CHECK THIS BOX IF THIS STATEMENT IS FILED PURSUANT TO RULE 13d-1(c)

ITEM 4. OWNERSHIP

            For information concerning the ownership of Common Stock of the
            Company by the Reporting Persons, see Items 5 through 9 and 11 of
            the cover pages to this schedule 13G and footnotes thereto.

ITEM 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS

            Not applicable

ITEM 6. OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON

            Not applicable

ITEM 7. IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE
        SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY

            Not Applicable

ITEM 8. IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP

            Not Applicable

ITEM 9. NOTICE OF DISSOLUTION OF GROUP


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            Not Applicable

ITEM 10. CERTIFICATION

            By signing below I certify that, to the best of my knowledge and
            belief, the securities referred to above 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
            a transaction having that purpose and effect.

                              SIGNATURES

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: February 10, 2001      By: /s/ Lindsay A. Rosenwald, M.D.
New York, NY                  Name: Lindsay A. Rosenwald, M.D.


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