Exhibit 99.1


CONTACT:
Justine E. Koenigsberg
Director, Corporate Communications
(617) 349-0271

FOR IMMEDIATE RELEASE

              TKT AND AVENTIS RECEIVE RECOMMENDATION FOR MARKETING
                    APPROVAL OF DYNEPO(TM) IN EUROPEAN UNION

CAMBRIDGE, MA, DECEMBER 12, 2001 -- Transkaryotic Therapies, Inc. (Nasdaq:
TKTX) today announced that the Committee for Proprietary Medicinal Products
of the European Agency for the Evaluation of Medicinal Products has issued a
positive opinion recommending approval of Dynepo(TM) (epoetin delta). Dynepo,
which is being developed with Aventis Pharma, is a human erythropoietin for
the treatment of anemia associated with renal disease. The CPMP
recommendation for approval will be forwarded to the European Commission for
final marketing authorization. If approved by the European Commission,
Aventis will be responsible for the marketing and distribution of Dynepo in
the fifteen countries of the European Union.

"We are pleased that our efforts with this clinical program have been
recognized. The CPMP's opinion allows us to move closer to making Dynepo
available as a treatment option for patients with anemia," said Helen Critchley,
Ph.D., Vice President, International Regulatory Affairs. "This recommendation
comes as a result of the hard work and cooperation of many people at both TKT
and Aventis."

TKT and Aventis are currently involved in litigation with both Amgen Inc. and
Kirin-Amgen, Inc. in regard to Dynepo. In April 2001, the High Court of Justice
in the United Kingdom ruled that one of four claims of a patent asserted by
Kirin-Amgen was infringed by TKT and Aventis in a separate patent suit involving
Dynepo. TKT and Aventis have filed an appeal in the case. The companies' ability
to market Dynepo will be dependent upon the outcome of the appeal proceeding.

Erythropoietin is a hormone that stimulates the production of red blood cells
and is used primarily as a treatment for anemia associated with kidney disease
or cancer chemotherapy. Dynepo is a human erythropoietin product produced using
TKT's proprietary gene activation technology. Dynepo has been tested in over
1400 dialysis and pre-dialysis patients as a treatment for anemia of renal
failure. A Phase III study is ongoing to test Dynepo for anemia associated with
cancer chemotherapy.

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Transkaryotic Therapies, Inc.
CPMP Recommends Approval of Dynepo
December 12, 2001
Page 2

ABOUT TKT

Transkaryotic Therapies, Inc. (TKT) is a biopharmaceutical company dedicated to
the development and commercialization of products based on its three proprietary
development platforms: Niche Protein(R) products, Gene-Activated(R) proteins,
and gene therapy. The Company's Niche Protein product platform is based on
protein replacement for the treatment of lysosomal storage disorders, a group of
rare genetic diseases characterized by the absence of certain metabolic enzymes.
TKT's gene activation technology is a proprietary approach to the large-scale
production of therapeutic proteins, which does not require the cloning of genes
and their subsequent insertion into non-human cell lines. The Company's gene
therapy technology, known as Transkaryotic Therapy(TM), is focused on the
commercialization of non-viral, EX VIVO gene therapy products for the long-term
treatment of chronic protein deficiency states.

THIS PRESS RELEASE CONTAINS FORWARD-LOOKING STATEMENTS THAT INVOLVE A NUMBER OF
RISKS AND UNCERTAINTIES. ANY STATEMENTS CONTAINED HEREIN THAT ARE NOT STATEMENTS
OF HISTORICAL FACT MAY BE DEEMED TO BE FORWARD-LOOKING STATEMENTS. WITHOUT
LIMITING THE FOREGOING, THE WORDS, "BELIEVES," "ANTICIPATES," "PLANS,"
"EXPECTS," "ESTIMATES," "INTENDS," "SHOULD," "COULD," "WILL," "MAY," AND SIMILAR
EXPRESSIONS ARE INTENDED TO IDENTIFY FORWARD-LOOKING STATEMENTS. THERE ARE A
NUMBER OF IMPORTANT FACTORS THAT COULD CAUSE THE COMPANY'S ACTUAL RESULTS TO
DIFFER MATERIALLY FROM THOSE INDICATED BY SUCH FORWARD-LOOKING STATEMENTS WHICH
ARE SET FORTH UNDER THE CAPTION "RISK FACTORS" IN THE COMPANY'S QUARTERLY REPORT
ON FORM 10-Q FOR THE QUARTER ENDED SEPTEMBER 30, 2001 WHICH IS ON FILE WITH THE
SECURITIES AND EXCHANGE COMMISSION AND INCORPORATED HEREIN BY REFERENCE. THESE
INCLUDE, WITHOUT LIMITATION, THE FOLLOWING: (1) WHETHER ANY OF THE COMPANY'S
NICHE PROTEIN, GENE-ACTIVATED PROTEIN, OR GENE THERAPY PRODUCT CANDIDATES WILL
ADVANCE IN THE CLINICAL TRIAL PROCESS, (2) WHETHER SUCH CLINICAL TRIALS WILL
PROCEED IN A TIMELY MANNER, (3) WHETHER THE CLINICAL TRIAL RESULTS WILL WARRANT
CONTINUED PRODUCT DEVELOPMENT, (4) WHETHER THE REQUIRED REGULATORY FILINGS, SUCH
AS INVESTIGATIONAL NEW DRUG APPLICATIONS AND BIOLOGICS LICENSE APPLICATIONS, ARE
MADE IN A TIMELY MANNER, (5) WHETHER THE COMPANY'S PRODUCTS WILL RECEIVE
APPROVAL FROM THE U.S. FOOD AND DRUG ADMINISTRATION OR EQUIVALENT FOREIGN
REGULATORY AGENCIES, (6) IF SUCH PRODUCTS RECEIVE APPROVAL, WHETHER THEY WILL BE
SUCCESSFULLY DISTRIBUTED AND MARKETED, (7) WHETHER PATENT LITIGATION IN WHICH
THE COMPANY IS INVOLVED OR MAY BECOME INVOLVED ARE RESOLVED IN A MANNER ADVERSE
TO THE COMPANY, (8) THE EFFECTS OF COMPETITIVE PRODUCTS ON THE COMPANY'S
PROPOSED PRODUCTS, AND (9) THE COMPANY'S DEPENDENCE ON THIRD PARTIES, INCLUDING
COLLABORATORS, MANUFACTURERS AND DISTRIBUTORS. IN ADDITION, ANY FORWARD-LOOKING
STATEMENTS REPRESENT THE COMPANY'S EXPECTATIONS ONLY AS OF THE DATE HEREOF AND
SHOULD NOT BE RELIED UPON AS REPRESENTING THE COMPANY'S EXPECTATIONS AS OF ANY
SUBSEQUENT DATE. WHILE THE COMPANY MAY ELECT TO UPDATE FORWARD-LOOKING
STATEMENTS AT SOME POINT IN THE FUTURE, THE COMPANY SPECIFICALLY DISCLAIMS ANY
OBLIGATION TO DO SO, EVEN IF ITS EXPECTATIONS CHANGE.


GENE-ACTIVATED(R), NICHE PROTEIN(R), AND TKT(R) ARE REGISTERED TRADEMARKS AND
TKT(TM) AND TRANSKARYOTIC THERAPY(TM) ARE TRADEMARKS OF TRANSKARYOTIC THERAPIES,
INC. DYNEPO(TM) IS A TRADEMARK OF AVENTIS PHARMA.

PLEASE VISIT OUR WEB SITE AT WWW.TKTX.COM FOR ADDITIONAL INFORMATION ABOUT
TRANSKARYOTIC THERAPIES, INC.

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