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

                                  SCHEDULE 13G
                    Under the Securities Exchange Act of 1934

                        Ligand Pharmaceuticals Incorporated
                                (Name of Issuer)

                                  Common Stock
                         (Title of Class of Securities)

                                    53220K207
                                 (CUSIP Number)

                                November 21, 2002

             (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)

[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 the
disclosures provided in a prior cover page.

The information required in 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).




CUSIP No. 53220K207

       1.    Names of Reporting Persons.
             I.R.S. Identification Nos. of above persons (entities only).

             OrbiMed Advisors Inc.

       2.    Check the Appropriate Box if a Member Of a Group (See Instructions)

             [ ] (a)
             [ ] (b)

       3.    SEC Use Only

       4.    Citizenship or Place of Organization

             Delaware

                   5.   Sole Voting Power           0
Number of
Shares             6.   Shared Voting Power         4,036,118
Beneficially
Owned by           7.   Sole Dispositive Power      0
Each Reporting
Person With        8.   Shared Dispositive Power    4,036,118

       9.    Aggregate Amount Beneficially Owned by Each Reporting Person
                       4,036,118

       10.   Check if the Aggregate Amount in Row (9) Excludes Certain Shares
             (See Instructions)

       11.   Percent of Class Represented by Amount in Row (9) 5.46%

       12.   Type of Reporting Person (See Instructions) IA

                                                                               2



CUSIP No. 53220K207

       1.    Names of Reporting Persons.
             I.R.S. Identification Nos. of above persons (entities only).

             OrbiMed Advisors LLC

       2.    Check the Appropriate Box if a Member of a Group (See Instructions)

             [ ] (a)
             [ ] (b)

       3.    SEC Use Only

       4.    Citizenship or Place of Organization

             Delaware

                   5.   Sole Voting Power           0
Number of
Shares             6.   Shared Voting Power         4,036,118
Beneficially
Owned by           7.   Sole Dispositive Power      0
Each Reporting
Person With        8.   Shared Dispositive Power    4,036,118

       9.    Aggregate Amount Beneficially Owned by Each Reporting Person
                       4,036,118

       10.   Check if the Aggregate Amount in Row (9) Excludes Certain Shares
             (See Instructions)

       11.   Percent of Class Represented by Amount in Row (9) 5.46%

       12.   Type of Reporting Person (See Instructions) IA

                                                                               3



CUSIP No. 53220K207

       1.    Names of Reporting Persons.
             I.R.S. Identification Nos. of above persons (entities only).

             Samuel D. Isaly

       2.    Check the Appropriate Box if a Member of a Group (See Instructions)

             [ ] (a)
             [ ] (b)

       3.    SEC Use Only

       4.    Citizenship or Place of Organization

             United States

                   5.   Sole Voting Power           0
Number of
Shares             6.   Shared Voting Power         4,036,118
Beneficially
Owned by           7.   Sole Dispositive Power      0
Each Reporting
Person With        8.   Shared Dispositive Power    4,036,118


       9.    Aggregate Amount Beneficially Owned by Each Reporting Person
                       4,036,118

       10.   Check if the Aggregate Amount in Row (9) Excludes Certain Shares
             (See Instructions)

       11.   Percent of Class Represented by Amount in Row (9) 5.46%

       12.   Type of Reporting Person (See Instructions) HC

                                                                               4



Item 1. (a)  Issuer: Ligand Pharmaceuticals Incorporated

        (b)  Address: 10275 Science Center Drive
                      San Diego, California  92121

Item 2. (a)  Name of Person Filing:
             OrbiMed Advisors Inc.
             OrbiMed Advisors LLC
             Samuel D. Isaly

        (b)  Address of Principal Business Offices:

             767 Third Avenue, 30th Floor
             New York, New York 10017

        (c)  Citizenship:
             Please refer to Item 4 on each cover sheet for each filing person

        (d)  Title of Class of Securities
             Common stock

        (e)  CUSIP Number: 53220K207

Item 3.  OrbiMed Advisors Inc. and OrbiMed Advisors LLC are investment advisors
         in accordance with ss.240.13-1 (b)(1)(ii)(E). Not applicable for Samuel
         D. Isaly.

Item 4.  Ownership

         Please see Items 5 - 9 and 11 for each cover sheet for each filing
         separately

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.

         Reporting persons are holding 5.46% of the securities on behalf of
         other persons who have the right to receive or the power to direct the
         receipt of dividends from or proceeds from sale of, such securities.

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

         Not Applicable

                                                                               5



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 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.

Date: November 29, 2002

                                                           OrbiMed Advisors Inc.

                                                  By: /s/ Samuel D. Isaly
                                                  ----------------------------
                                                  Name:  Samuel D. Isaly
                                                  Title: President

                                                            OrbiMed Advisors LLC

                                                  By: /s/ Samuel D. Isaly
                                                  ----------------------------
                                                  Name:  Samuel D. Isaly
                                                  Title: Managing Member

                                                                 Samuel D. Isaly

                                                  By: /s/ Samuel D. Isaly
                                                  ----------------------------
                                                  Name:  Samuel D. Isaly



         By signing below I certify that, to the best of my knowledge and
         belief, the securities referred to above were acquired and 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.

Date: November 29, 2002

                                                            OrbiMed Advisors Inc

                                                  By: /s/ Samuel D. Isaly
                                                  ----------------------------
                                                  Name:  Samuel D. Isaly
                                                  Title: President

                                                                               6



                                                            OrbiMed Advisors LLC

                                                  By: /s/ Samuel D. Isaly
                                                  ----------------------------
                                                  Name:  Samuel D. Isaly
                                                  Title: Managing Member

                                                                 Samuel D. Isaly

                                                  By: /s/ Samuel D. Isaly
                                                  ----------------------------
                                                  Name:  Samuel D. Isaly


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