1 UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G/A UNDER THE SECURITIES EXCHANGE ACT OF 1934 (AMENDMENT NO. 1)* ALEXION PHARMACEUTICALS, INC. - ------------------------------------------------------------------------------- (Name of Issuer) COMMON STOCK, PAR VALUE $.0001 PER SHARE - ------------------------------------------------------------------------------- (Title of Class of Securities) 015351109 -------------------------- (CUSIP Number) - ------------------------------------------------------------------------------- (Date of Event Which Requires Filing 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 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). Page 1 of 6 pages
2 CUSIP No. 015351109 - ------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). BB BIOTECH AG - ------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a) [X] (b) [] - ------------------------------------------------------------------------------- 3. SEC Use Only - ------------------------------------------------------------------------------- 4. Citizenship or Place of Organization SWITZERLAND - ------------------------------------------------------------------------------- Number of 5. Sole Voting Power Shares Beneficially -0- Owned by Each Reporting ------------------------------------------------------- Person With: 6. Shared Voting Power 874,113 ------------------------------------------------------- 7. Sole Dispositive Power -0- ------------------------------------------------------- 8. Shared Dispositive Power 874,113 - ------------------------------------------------------------------------------- 9. Aggregate Amount Beneficially Owned by Each Reporting Person 874,113 10. Check if the Aggregate Amount in Row (11) Excludes Certain shares 11. Percent of Class Represented by amount in Row (11) 4.9% - ------------------------------------------------------------------------------- 12. Type of Reporting Person (See Instructions) HC, CO - ------------------------------------------------------------------------------- Page 2 of 6 pages
3 CUSIP No. 015351109 - ------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). BIOTECH TARGET S.A. - ------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (a) [X] (b) [] - ------------------------------------------------------------------------------- 3. SEC Use Only - ------------------------------------------------------------------------------- 4. Citizenship or Place of Organization PANAMA - ------------------------------------------------------------------------------- Number of 5. Sole Voting Power Shares Beneficially -0- Owned by Each Reporting ------------------------------------------------------- Person With: 6. Shared Voting Power 874,113 ------------------------------------------------------- 7. Sole Dispositive Power -0- ------------------------------------------------------- 8. Shared Dispositive Power 874,113 - ------------------------------------------------------------------------------- 9. Aggregate Amount Beneficially Owned by Each Reporting Person 874,113 10. Check if the Aggregate Amount in Row (11) Excludes Certain shares 11. Percent of Class Represented by amount in Row (11) 4.9% - ------------------------------------------------------------------------------- 12. Type of Reporting Person CO - ---------------------------------------------------------------------------- Page 3 of 6 pages
4 CUSIP No. 015351109 - ------------------------------------------------------------------------------- ITEM 2. (a) Name of Person Filing BB Biotech AG ("BB Biotech") Biotech Target S.A. ("Biotech Target") (b) Address of Principal Business Office or, if none, Residence BB Biotech Biotech Target Vordergasse 3 Swiss Bank Tower 8200 Schaffhausen Panama 1 CH/Switzerland Republic of Panama (c) Citizenship See Item No. 4 of cover pages. (d) Title of Class of Securities Common Stock, Par Value $.0001 Per Share (e) CUSIP Number 015351109 ITEM 4. OWNERSHIP Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1. (a) Amount beneficially owned: 874,113 (b) Percent of class: 4.9% (c) Number of shares as to which the person has: (i) Sole power to vote or to direct the vote -0- (ii) Shared power to vote or to direct the vote 874,113 (iii) Sole power to dispose or to direct the disposition of -0- (iv) Shared power to dispose or to direct the disposition of 874,113 ITEM 5. Ownership of Five Percent or Less of a Class If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following: [ X ] ITEM 7. IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY This statement is filed jointly by BB Biotech and Biotech Target. Biotech Target is a wholly-owned subsidiary of BB Biotech. Page 4 of 6 pages
5 CUSIP No. 015351109 - ------------------------------------------------------------------------------- SIGNATURES After reasonable inquiry and the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. BB BIOTECH AG Date: February 14, 2001 By: /s/ Dubravka Racjnak --------------------- Name: Dubravka Racjnak --------------------- Title: Signatory Authority --------------------- Date: February 14, 2001 By: /s/ Anders Hove --------------------- Name: Anders Hove --------------------- Title: Signatory Authority --------------------- BIOTECH TARGET S.A. Date: February 14, 2001 By: /s/ Dubravka Racjnak --------------------- Name: Dubravka Racjnak --------------------- Title: Signatory Authority --------------------- Date: February 14, 2001 By: /s/ Anders Hove --------------------- Name: Anders Hove --------------------- Title: Signatory Authority --------------------- Page 5 of 6 pages
6 CUSIP No. 015351109 - ------------------------------------------------------------------------------- EXHIBIT INDEX ------------- Exhibit 1: Agreement by and between BB Biotech and Biotech Target with respect to the filing of this disclosure statement.* - --------------------- * Previously filed. Page 6 of 6 pages