SEC 1473
(09-02)

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

 1. Name and Address of Reporting Person*

Ambrosio       Costantino                  

(Street)

(City)      (State)          (Zip)

 3. I.R.S. Identification
    Number of Reporting
    Person, if an entity
    (voluntary)

 5. Relationship of Reporting Person(s) to Issuer

  (Check all applicable)

 X  Director

      10% Owner

 X  Officer (give title below)

      Other (specify below)

 6. If Amendment,
    Date of Original
    (Month/Day/Year)

 7. Individual or Joint/Group

    Filing (Check Applicable Line)

 X  Form filed by One Reporting Person

      Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned

 1. Title of Security
    (Instr. 4)

 2.  Amount of
    Securities
    Beneficially
    Owned
    (Instr. 4)

 3. Ownership Form: Direct (D) or Indirect (I)
    (Instr. 5)

 4. Nature of Indirect Beneficial Ownership
    (Instr. 5)

Common stock

141,600

D

Table II - Derivative Securities Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of
    Derivative
    Security
    (Instr. 4)

2.  Date Exercisable and
    Expiration Date
    (Month/Day/Year)

3. Title and Amount of
    Securities Underlying Derivative
    Security (Instr. 4)

4. Conversion or
    Exercise Price of
    Derivative
    Security

5. Ownership
    Form of Derivative
    Securities: Direct (D)
    or Indirect (I) (Instr. 5)

6. Nature of Indirect
    Beneficial
    Ownership
    (Instr. 5)

Date Exercisable

Expiration Date

Title

Amount or
Number of Shares

Option to purchase common stock

(1)

(1)

Common stock

88,500

$10.62

D

Option to purchase common stock

(2)

(2)

Common stock

400,000

$10.62

D

Explanation of Responses:

(1)                                  This option was granted by Versicor on March 1, 2003 (Italy time, or February 28, 2003 Pennsylvania time) under its 2002 Stock Option Plan as a replacement stock option upon the effectiveness of the merger between Versicor and Biosearch Italia.  Subject to continued service as a director, the option vests as to 25% of the underlying shares 12 months after the date of grant and the balance of 75% vests in 36 equal monthly installments (with each installment vesting on the 28th day of each month) commencing 13 months after the date of grant.

(2)                                  This option was granted by Versicor on March 1, 2003 (Italy time, or February 28, 2003 Pennsylvania time) under its 2001 Stock Option Plan.  Subject to continued service as a director, the option vests as to 25% of the underlying shares 12 months after the date of grant and the balance of 75% vests in 36 equal monthly installments (with each installment vesting on the 28th day of each month) commencing 13 months after the date of grant.

Peter T. Healy, Esq. (by power of attorney)

4/16/03

** Signature of Reporting Person

Date

*

If the form is filed by more than one reporting person, see Instruction 5(b)(v).

**

Intentional misstatements or omissions of facts constitute Federal Criminal Violations.  See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note:

File three copies of this Form, one of which must be manually signed. If space is insufficient,

See Instruction 6 for procedure.