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

                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934



                          DISCOVERY LABORATORIES, INC.
                                (Name of Issuer)

                                  Common Stock
                         (Title of Class of Securities)

                                   254668 10 6
                                 (CUSIP Number)

                                  July 30, 1999
             (Date of Event which Requires Filing of this Statement)

         Check the appropriate box to designate the rule pursuant to which this
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 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).


CUSIP No. 254668 10 6 (1) Name of Reporting Person S.S. or I.R.S. Identification No. of Above Person OrbiMed Advisors LLC ----------------------------------------------------------------------- (2) Check the Appropriate Box if a Member of Group (See Instructions) [ ] (a) [ ] (b) ----------------------------------------------------------------------- (3) SEC Use Only ----------------------------------------------------------------------- (4) Citizenship or Place of Organization Delaware ----------------------------------------------------------------------- Number of (5) Sole Voting Power 0 Shares Beneficially ------------------------------------------------------------- Owned by (6) Shared Voting Power 1,687,603 Each Reporting ------------------------------------------------------------- Person (7) Sole Dispositive Power 0 With ------------------------------------------------------------- (8) Shared Dispositive Power 1,687,603 ----------------------------------------------------------------------- (9) Aggregate Amount Beneficially Owned by Each Reporting Person 1,687,603 ----------------------------------------------------------------------- (10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) ----------------------------------------------------------------------- (11) Percent of Class Represented by Amount in Row (9) 17.4% ----------------------------------------------------------------------- (12) Type of Reporting Person (See Instructions) CO ---------------------------

CUSIP No. 254668 10 6 (1) Name of Reporting Person S.S. or I.R.S. Identification No. of Above Person Caduceus Capital Trust ----------------------------------------------------------------------- (2) Check the Appropriate Box if a Member of Group (See Instructions) [ ] (a) [ ] (b) ----------------------------------------------------------------------- (3) SEC Use Only ----------------------------------------------------------------------- (4) Citizenship or Place of Organization Bermuda ----------------------------------------------------------------------- Number of (5) Sole Voting Power 0 Shares Beneficially ------------------------------------------------------------- Owned by (6) Shared Voting Power 1,687,603 Each Reporting ------------------------------------------------------------- Person (7) Sole Dispositive Power 0 With ------------------------------------------------------------- (8) Shared Dispositive Power 1,687,603 ----------------------------------------------------------------------- (9) Aggregate Amount Beneficially Owned by Each Reporting Person 1,687,603 ----------------------------------------------------------------------- (10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) ----------------------------------------------------------------------- (11) Percent of Class Represented by Amount in Row (9) 17.4% ----------------------------------------------------------------------- (12) Type of Reporting Person (See Instructions) OO ---------------------------

CUSIP No. 254668 10 6 (1) Name of Reporting Person S.S. or I.R.S. Identification No. of Above Person Caduceus Capital II, L.P. ----------------------------------------------------------------------- (2) Check the Appropriate Box if a Member of Group (See Instructions) [ ] (a) [ ] (b) ----------------------------------------------------------------------- (3) SEC Use Only ----------------------------------------------------------------------- (4) Citizenship or Place of Organization Delaware ----------------------------------------------------------------------- Number of (5) Sole Voting Power 0 Shares Beneficially ------------------------------------------------------------- Owned by (6) Shared Voting Power 1,687,603 Each Reporting ------------------------------------------------------------- Person (7) Sole Dispositive Power 0 With ------------------------------------------------------------- (8) Shared Dispositive Power 1,687,603 ----------------------------------------------------------------------- (9) Aggregate Amount Beneficially Owned by Each Reporting Person 1,687,603 ----------------------------------------------------------------------- (10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) ---------------------------------------------------------------------- (11) Percent of Class Represented by Amount in Row (9) 17.4% ---------------------------------------------------------------------- (12) Type of Reporting Person (See Instructions) PN ---------------------------

CUSIP No. 254668 10 6 (1) Name of Reporting Person S.S. or I.R.S. Identification No. of Above Person Finsbury Worldwide Pharmaceutical Trust ----------------------------------------------------------------------- (2) Check the Appropriate Box if a Member of Group (See Instructions) [ ] (a) [ ] (b) ----------------------------------------------------------------------- (3) SEC Use Only ----------------------------------------------------------------------- (4) Citizenship or Place of Organization United Kingdom ----------------------------------------------------------------------- Number of (5) Sole Voting Power 0 Shares Beneficially ------------------------------------------------------------- Owned by (6) Shared Voting Power 1,687,603 Each Reporting ------------------------------------------------------------- Person (7) Sole Dispositive Power 0 With ------------------------------------------------------------- (8) Shared Dispositive Power 1,687,603 ----------------------------------------------------------------------- (9) Aggregate Amount Beneficially Owned by Each Reporting Person 1,687,603 ----------------------------------------------------------------------- (10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) ----------------------------------------------------------------------- (11) Percent of Class Represented by Amount in Row (9) 17.4% ----------------------------------------------------------------------- (12) Type of Reporting Person (See Instructions) OO ---------------------------

Item 1. Issuer (a) Discovery Laboratories, Inc. (b) 350 South Main Street, Suite 307, Doylestown, PA 18901 Item 2. Persons Filing (a) Name of Persons Filing: OrbiMed Advisors LLC Caduceus Capital Trust Caduceus Capital II, L.P. Finsbury Worldwide Pharmaceutical Trust (b) Address of Principal Offices: c/o OrbiMed Advisors LLC 767 Third Avenue, 6th Floor New York, New York 10010 (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: 254668 10 6 Item 3. Not Applicable Item 4. Ownership Please see Items 5, 6, 7, 8, 9, and 11 for each cover sheet for each filing entity. 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 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 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, 1999 ORBIMED ADVISORS LLC By: /s/ Samuel D. Isaly --------------------------------- Name: Samuel D. Isaly Title: Managing Member CADUCEUS CAPITAL TRUST By: /s/ Deborah O'Donnel --------------------------------- Name: Deborah O'Donnel Title: Secretary CADUCEUS CAPITAL II, L.P. By: OrbiMed Advisors LLC, its general partner By: /s/ Samuel D. Isaly ---------------------------- Name: Samuel D. Isaly Title: Managing Member FINSBURY WORLDWIDE PHARMACEUTICAL TRUST By: /s/ Samuel D. Isaly --------------------------------- Name: Samuel D. Isaly Title: Director