| Glaxo-Wellcome have just
released details of their phase II studies into "Dutasteride
(GI198745)" a dual 5-alpha-reductase inhibitor at the
American Academy of Dermatology (AAD) meeting in San
Francisco.
Propecia (Finasteride), the latest approved
medication for hair loss, inhibits one of the two types of
this enzyme which turns Testosterone into DHT. Dutasteride,
the medication discussed in this article, blocks both types of
the enzyme and so it is believed it will be more effective at
treating hair loss.
The Phase II studies involved 416 men aged
21-45 with Norwood patterns IIIv, IV, and V. The study lasted
for 6 months and was randomized and double-blind (meaning the
investigators did not know who was getting which medication).
Placebo and Proscar were compared to 0.05, 0.1, 0.5, and 2.5mg
of Dutasteride. Proscar (the 5mg form of Finasteride -
Propecia is the 1mg form) was used because Propecia was not
available at the time the studies started.
Very little Dutasteride is required to
inhibit type 1 5-alpha-reductase but very large quantities of
Propecia are required to do so. For type 2 5-alpha reductase
(the one Propecia blocks), even less Dutasteride is required
to block it than Propecia. So small doses of Dutasteride
provide very good inhibition of both types of the 5-alpha
reductase enzyme.
There were no results presented on efficacy
but sexual side effects have occurred in the studies.
Dutasteride at this point remains on hold
for Phase III studies. It is unknown why the company has not
decided yet whether to proceed with Phase III trials. The two
most likely reasons may be that either the company believes
the drug will not make enough money if released (Propecia
sales have been described as disappointing in several press
articles evaluating sales) or that the company does not
believe the treatment will be approved for the cosmetic
purpose of hair loss due to side effects. Glaxo-Wellcome made
a statement that a decision would be made in February
regarding the trials, however to date no decision has been
publicly announced.
The good news is that Phase III trials have
already been completed for Benign Prostatic Hyperplasia (BPH,
also known as enlarged prostates) and the drug is scheduled to
be submitted to the FDA for approval sometime this year and
approved and marketed sometime next year. Finasteride followed
a similar course and was first approved for BPH and then later
for hair loss.
 |
