Eight drug and diagnostic makers are using Enzon Inc.'s single-chainantigen-binding (SCA) protein technology in their productdevelopment, but the newest licensee, Rhone-Poulenc Rorer Inc., isthe first to apply it to cell and gene therapy.

SCA proteins, which are engineered forms of monoclonal antibodies,include the binding portion only of monoclonals and attachthemselves to specific antigen targets. Because they are smaller andlighter, SCA proteins can go places conventional monoclonalantibodies cannot and can be modified more easily to boostperformance and reduce adverse side effects.

Donna Brasco, spokeswoman for Enzon, said SCA proteins are beingdeveloped to deliver imaging agents for cancer detection andtherapeutics, such as chemotherapy drugs, for battling the disease.

Rhone-Poulenc Rorer, of Collegeville, Pa., also initially will targetcancer with the SCA proteins, but it intends to use them inside cellsto counteract proteins linked to the disease, such as those expressedby oncogenes.

The proposed therapy involves using viral or non-viral vectors toinsert in targeted cells genetic material created to express a specificSCA protein, which would then seek out and neutralize the harmfulcellular activity.

Jo Bossart, Rorer's vice president of business and marketingdevelopment, said the company may be ready for clinical trials at theend of 1996 with an oncogene-inhibiting SCA protein.

The Rorer program will be conducted within the Gencell division,which was formed in 1994 to develop cell and gene therapy products.Gencell is a network of 14 companies and academic institutionsheadquartered in Santa Clara, Calif.

Rorer paid $1 million to Enzon for a non-exclusive license to useSCA proteins. The agreement also would pay Enzon milestones androyalties as drugs are developed.

Other pharmaceutical companies working with Enzon's SCA proteintechnology include Eli Lilly and Co., of Indianapolis, Bristol-MyersSquibb Co., of New York, and Baxter Healthcare Corp., of Deerfield,Ill.

Brasco said those three companies are still in the research stage withtheir applications of the technology.

She said the most advanced drug candidate, SCA CC49, is an SCAprotein coupled with a monoclonal antibody for treatment ofcolorectal cancer. The product is in Phase I studies conducted by theNational Institutes of Health, of Bethesda, Md., and Enzon.

Brasco said the non-exclusive licenses and collaborations for SCAprotein technology have not yet generated significant income.However, all the agreements include milestone payments androyalties on products developed.

In addition to the $1 million paid by Rorer, Bristol-Myers paid $1.8million in August 1994 to use the technology for its cancer drugdevelopment.

Enzon, of Piscataway, N.J., acquired the SCA protein technology in1991 when it took over Genex Corp., of Gaithersburg, Md. Brascosaid Enzon decided to license out the technology rather than build aproduct development program around it.

Enzon's own drug development is focused on another deliverytechnology that combines polyethylene glycol (PEG) with atherapeutic agent. It has two products on the U.S. market. PEG-adenosine deaminase is sold by Enzon as Adagen for treatment ofsevere combined immunodeficiency disease and PEG-L asparaginaseenzyme is marketed as Oncaspar by Rorer for acute lymphoblasticleukemia. n

-- Charles Craig

(c) 1997 American Health Consultants. All rights reserved.