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                                                                   EXHIBIT 10.11

                      AMENDMENT NO. 1 TO SERVICE AGREEMENT


               This Amendment No. 1 to Service Agreement (the "Amendment") is
made between Seragen, Inc., a Delaware corporation having a usual place of
business at 97 South Street, Hopkinton, Massachusetts ("Seragen"), and Marathon
Biopharmaceuticals, LLC, a Massachusetts limited liability company having a
usual place of business at 97 South Street, Hopkinton, Massachusetts (the
"Service Provider"), as successor by assignment of Trustees of Boston University
("BU"), as of May 11, 1998, for the purpose of amending that certain Service
Agreement, dated as of February 14, 1997 (the "Service Agreement"), between
Seragen and BU.

               This Amendment is made with reference to the following facts:

               A. Seragen entered into the Service Agreement to purchase certain
services relating to product research, development, manufacturing, clinical
trial, quality control, and quality assurance.

               B. Service Provider is the successor by assignment to BU, one of
the original parties to the Service Agreement.

               C. Seragen has made certain business decisions that will result
in a reduction of the amount of product research, development, manufacturing,
clinical trial, quality control, and quality assurance services that will be
required in the second Contract Year (as defined in the Service Agreement).

               D. Seragen is willing, on the terms set forth in this Amendment,
to perform for itself certain clinical trial services originally subject to the
Service Agreement and Service Provider desires to make available to Seragen the
assets necessary for Seragen to perform those services.

               E. Section 2.01 of the Service Agreement provides that, in the
event that Seragen's research and development requirements change, the parties
to the Service Agreement shall negotiate amendments (including appropriate price
reductions) to the services required to be performed under the Service
Agreement. Section 4.01 of the Service Agreement provides that, in such an
event, the parties shall agree on appropriate adjustments to the Technology
Service Fees (as defined in the Service Agreement) payable under the Service
Agreement; provided, however, that in no event shall the Technology Service Fees
payable with respect to any Contract Year be reduced to less than $4,300,000.

               NOW, THEREFORE, in consideration of the mutual covenants and
agreements contained in this Amendment, the parties to this Amendment, intending
to be legally bound, agree as follows:


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               1. In lieu of the services required to be provided pursuant to
Schedule 1 to the Service Agreement by Service Provider in the second Contract
Year, Service Provider shall provide the services specified in Schedule 1
attached to this Amendment.

               2. In light of the reduced services to be provided to Seragen in
the second Contract Year, the Technology Service Fees for the second Contract
Year shall be $4,300,000.

               3. Service Provider shall make available without any additional
compensation to Seragen all assets necessary for Seragen to perform such
clinical trial services at the facility located at 99 South Street, Hopkinton,
Massachusetts, as Seragen may from time to time reasonably specify, which
services are not required to be performed by Service Provider under this
Amendment.

               4. Capitalized terms used in this Amendment and not otherwise
defined shall have the meaning given those terms in the Service Agreement.

               5. Except as expressly modified by this Amendment, the Service
Agreement shall remain in full force and effect.


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               Seragen and Service Provider have executed this Amendment
effective as of the date first set forth above.

                                  SERAGEN, INC.



                                        /s/ Reed R. Prior
                                    ---------------------------------
                                    By:     Reed R. Prior
                                            Chairman, Chief Executive
                                            Officer & Treasurer



                                    MARATHON BIOPHARMACEUTICALS, LLC
                                    Service Provider


                                        /s/ Kenneth G. Condon
                                    ---------------------------------
                                    By:     Kenneth G. Condon
                                            Manager
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                          SCHEDULE 1- SERVICE AGREEMENT


SERVICES TO BE PERFORMED BY SERVICE PROVIDER FOR SERAGEN IN 1998:


MANUFACTURING OF BATCHES - 1998:

                                                                       ORIGINAL
                                                                       ESTIMATED
                                                                      COMPLETION
SERVICE                                 SPECIFICATIONS                   DATE        CURRENT PLANS FOR 1998        COMMENTS
                                                                                                          
                                                                                                                                    
Fermentation cost of 6 batches of       Master Batch Record 22-004,      Q4 98              Q2 98            Fermentation plans from
DAB389IL-2                              30-004                                                               1997 to be conducted in
                                                                                                             Q1/Q2 1998 for PAI will
                                                                                                               provide sufficient   
                                                                                                                    inventory       
                                                                                                   
Purification cost of 10 batches of      Master Batch Record 31-304,      Q2 98           Eliminated          Sufficient inventories 
2nd Generation - DAB389IL-2             32-304, 34-304, 60-304                                                for clinicals permit 
                                                                                                                  shift to 1999     

Purification cost of 13 batches of      Master Batch Record 31-004,      Q3 98              Q2 98            Purification plans from
1st Generation - DAB389IL-2             32-004, 60-104                                                       1997 to be conducted in
                                                                                                             Q1/Q2 1998 for PAI will
                                                                                                               provide sufficient   
                                                                                                               inventory to cover   
                                                                                                                 product launch     
                                                                                                             

Fermentation cost of 5 batches of       Master Batch Record 22-007,                         Q3 98 
DAB389EGF*                              24-007                                                                                      
                                                                                                             
Purification cost of 10 batches of      Master Batch Record 31-007,                         Q4 98                            
DAB389EGF*                              34-007, 44-007, 47-007,                                                                     
                                        65-007, 66-007 and 70-007                                                         
Manufacture of formulation buffer*                                                          Q1 98                For Lilly PAI
                                                                                                  
                                                                                                                                    
        Includes raw materials, labor and utilities                                                                                 
                                                                                                                                    
                                                                                                                                    


                              Schedule 1 - Page 1
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                          SCHEDULE 1- SERVICE AGREEMENT


SERVICES TO BE PERFORMED BY SERVICE PROVIDER FOR SERAGEN IN 1998:

MANUFACTURING FILL OF BATCHES - 1998:

                                                          ORIGINAL
                                                         ESTIMATED
SERVICE                   SPECIFICATIONS               COMPLETION DATE     CURRENT PLANS FOR 1998                COMMENTS
                                                                                               
                                                                                     
Fill of DAB389EGF         Performed at fill-finish         Q4 98                 Eliminated                  Shift to Q2 99
                          site following their                   
                          Master Batch Record(s).                
                          Prior to fill,                         
                          formulation performed at               
                          Service Provider                                                                    
                          following Master Batch   
                          Record 65-007, 66-007,   
                          70-007.                  
                          

Fill of DAB389IL-2        Performed at fill-finish         Q4 98             1 - 4 fills between        Fills planned for 1997 to 
1st Generation            site following their                                   Q2 - Q4 98               be conducted in Q3/Q4   
                          Master Batch Records(s)                                                           1998 will provide     
                                                                                                        sufficient inventory to  
                                                                                                         cover product launch    
                                                                                                 

Fill of DAB389IL-2        Performed at fill-finish         Q4 98                 Eliminated                  Shift to Q2 99
2nd Generation            site following their                                     
                          Master Batch Record(s).  
                          Prior to fill 
                          formulation performed at    
                          Service Provider                 
                          following Master Batch Record
                          70-304, 70-404.

Fill of formulation 
buffer for PAI*                                            Q2 98



                              Schedule 1 - Page 2


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                                SCHEDULE 1- SERVICE AGREEMENT


Shipment of bulk to fill       
sites. Storage of fermentation 
pellets, purified drug         
substance, in process samples  
and final drug product         
(clinical trial material       
only). Shipment of clinical    
trial material to clinical     
sites (also return,            
accountability). Shipment of   
material to sites for          
non-clinical use. Label        
control for clinical and       
non-clinical materials (i.e.   
not market product)*           




SERVICES TO BE PERFORMED BY SERVICE PROVIDER FOR SERAGEN IN 1998:


QUALITY CONTROL AND RELEASE TESTING OF BATCHES - 1998:

                                                                            ORIGINAL
                                                                            ESTIMATED
                                                                           COMPLETION
SERVICE                                     SPECIFICATIONS                    DATE           CURRENT PLANS FOR 1998      COMMENTS
                                                                                                            

QC testing of 6 fermentation batches        Product spec. 30-004         Q4 98 - ongoing       Q2 98 - ongoing
of DAB389IL-2

QC testing of 13 purification batches       Product spec. 60-304         Q4 98 - ongoing       Q2 98 - ongoing
of 1st Generation DAB389IL-2

QC testing of 5 fermentation batches                                                               Q3 98
of DAB389EGF*

QC testing of 10 purification batches       Product spec. 60-007         Q4 98 - ongoing       Q4 98 - ongoing
of DAB389EGF

QC testing of Fills, DAB389IL-2             Product spec. 90-204-02      Q4 98 - ongoing       Q2 98 - ongoing
1st Generation

QC testing of Fills, DAB389IL-2             Product spec. 70-304 and     Q4 98 - ongoing         Eliminated            Shift to 1999
2nd Generation                              91-304-01; 5 mg/ml

QC testing of Fills, DAB389IL-2             Product spec. 70-404 and     Q4 98 - ongoing         Eliminated            Shift to 1999
2nd Generation                              91-404-02; 150 ug/ml

QC testing of Fills, DAB389EGF              Product spec. 70-007 and     Q4 98 - ongoing         Eliminated            Shift to 1999
                                            91-007



                              Schedule 1 - Page 3

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                          SCHEDULE 1- SERVICE AGREEMENT


                                                                                            
Stability testing of                                              Q4 98 - ongoing     Q1 98 - on-going
DAB389IL-2 and DAB389EGF 
products held by service 
provider for Seragen     

Includes raw materials, labor
and overhead



SERVICES TO BE PERFORMED BY SERVICE PROVIDER FOR SERAGEN IN 1998:


QUALITY ASSURANCE - 1998:




                                                                 ORIGINAL
                                                                 ESTIMATED
                                                                COMPLETION
SERVICE                              SPECIFICATIONS                DATE           CURRENT PLANS FOR 1998         COMMENTS
                                                                                                            

Documentation and auditing                                        Q4 98              Q1 98 - on-going
(audit report) specific to the 
products in Manufacturing and   
Product Development. Review    
and approval of all Master     
Batch Records, SOPs and        
reports as listed in services  
agreement.                     


Certificate of Analysis and         Appropriate SOP's and         Q4 98                  On-going
release notification for            release documents
batches and lots listed in  
services agreement          


Provide copies of all        
manufacturing records,       
laboratory records, deviation
reports and other records and
documents to Seragen for     
review*                      



               Schedule 1 - Page 4


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                          SCHEDULE 1- SERVICE AGREEMENT



Provide reports, data and other
information needed for Seragen to assess
compliance with regulatory requirements*


Preparation for PAI - implement audit -
specified and other changes to GMP
systems, procedures and documents as
necessary to prepare for FDA inspection.
Provide periodic progress reports to
Seragen. Notify Seragen of any
significant issues impacting on ability
to correct deficiencies and prepare for
inspections*

Includes raw materials, labor and overhead


SERVICES TO BE PERFORMED BY SERVICE PROVIDER FOR SERAGEN IN 1998:


 PRODUCT DEVELOPMENT - 1998:



                                                                             ORIGINAL
                                                                             ESTIMATED
                                                                            COMPLETION
SERVICE                                             SPECIFICATIONS             DATE          CURRENT PLANS FOR 1998       COMMENTS
                                                                                                              

2nd Generation; improve lyophilization                    -                    Q2 98                Eliminated
and characterization of new  DMF

EGF process development continue responses                -                    Q4 98                Eliminated
for BLA

Development of topical formulations and                   -                    Q4 98                Eliminated
new molecules

        Includes labor and direct materials



                              Schedule 1 - Page 5

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                                SCHEDULE 1- SERVICE AGREEMENT



SERVICES TO BE PERFORMED BY SERVICE PROVIDER FOR SERAGEN IN 1998:

 CLINICAL / PRE-CLINICAL / REGULATORY STUDIES - 1998:


 
                                                       ORIGINAL
                                                       ESTIMATED
                                                      COMPLETION
SERVICE                        SPECIFICATIONS            DATE       CURRENT PLANS FOR 1998                COMMENTS
                                                                                      

Phase I/II Psoriasis*          Protocol 96-04-21                        Trial on-going           Trial on-going - estimated
                                                                                                      completion Q4 98

Phase I/II Psoriasis           Protocol 96-04-19        Q2 97           Trial on-going           Trial on-going - estimated
                                                                                                      completion Q4 98

Phase I (SC) Psoriasis         Protocol 98-08-01        Q3 98                Q3 98              Estimated start - Q3 98 with
                                                                                                      completion Q3 99



                              Schedule 1 - Page 6

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                          SCHEDULE 1- SERVICE AGREEMENT


                                                                                          
Phase I/II EGF                     Protocol 96-02-03             Q3 97         Trial on-going        Trial on-going - estimated
                                                                                                          completion Q4 98

Limited use - Rheumatoid           Protocol 95-04-18                           Trial on-going              Trial on-going
Arthritis*


Phase I 2nd Generation                     -                     Q1 98           Eliminated
Psoriasis


Phase II/III NHL                           -                     Q4 98           Eliminated


Phase I (SC) Derm                          -                     Q4 98           Eliminated


Phase I/II (IV) Other                      -                     Q4 98           Eliminated


        Includes clinical trail site fees, labs, pathology fees, supplies and
overhead, clinical assays


SERVICES TO BE PERFORMED BY SERVICE PROVIDER FOR SERAGEN IN 1998:


 CLINICAL / PRE-CLINICAL / REGULATORY STUDIES AND OTHER- 1998:



                                                                      ORIGINAL
                                                                      ESTIMATED
                                                                     COMPLETION
SERVICE                           SPECIFICATIONS                        DATE         CURRENT PLANS FOR 1998              COMMENTS
                                                                                                        
CTCL trials: service provider    -Protocols for studies 93-04-11,       Q4 98              On-going             Estimated completion
labor and outside contract       93-04-14                                                                              date Q2
labor CTCL                                                                                                                00
Non-Besselaar contracts                                                                                                    

Pre-Clinical studies: new                                               Q4 98            Eliminated
refold 2nd generation and    
EGF studies - includes labor,  
supplies and overhead          



                              Schedule 1 - Page 7

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                          SCHEDULE 1- SERVICE AGREEMENT


* Services were included in original Schedule 1 to Service Agreement but are
being specifically mentioned in this amendment for clarity.

PRICE FOR SERVICES RENDERED IN 1997 - $6,605,651(Original estimate) 

PRICE FOR SERVICES RENDERED IN 1997 - $4,300,000 (Revised estimate)


Initials:


- ---------------       ----------------      ---------------  
Pat Bacha             Elizabeth Chen        Jean Nichols        


- ---------------       ----------------     
John O'Loughlin       Tony Rotunno

                              Schedule 1 - Page 8