Monday, November 25, 1996
A few years ago, there was little in the way of treatment options
to offer AIDS patients with cytomegalovirus retinitis. The situation is different
today, with five products on the market: Roche's Cytovene intravenous ganciclovir
and oral ganciclovir, Astra's iv Foscavir foscarnet, Chiron Corp.'s Vitrasert
intravitreal implant with ganciclovir, and Gilead Sciences Inc.'s Vistide cidofovir.
Most recent to market is Vistide, a nucleotide analog approved
in June. Now that Vistide has been on the market long enough for physicians
to begin to become familiar with it, BioCentury asked clinicians to discuss
their treatment decisions for patients. In addition, they were asked to describe
how the success of drug cocktails for AIDS patients, including drugs such as
protease inhibitors and BioChem Pharma Inc.'s Epivir 3TC, has changed the course
of CMV in their patients.
CMV is the most common viral opportunistic infection in AIDS,
affecting about 90 percent of patients, with about 20-40 percent of AIDS patients
getting CMV retinitis in the eye.
CHIR's Vitrasert, which was approved in March, posted $4.8
million in second quarter sales and $3.3 million in third quarter sales. It
is co-promoted worldwide by Chiron Vision and F. Hoffmann-La Roche Ltd. (Basel,
GILD's Vistide ran up just under $4 million in third quarter
sales. According to spokesperson Lana Lauher, as of Sept. 30, Vistide had captured
10 percent of the CMV market if oral ganciclovir is included, and 16 percent
of the market for iv therapies. GILD estimates that more than 1,500 patients
were on the commercial product (as opposed to patients in trials receiving free
drug) as of Sept. 30.
None of the drugs is perfect, and conversations with clinicians
make it clear that there will be no single winner: some drugs will be more appropriate
for certain patients than others.
Further complicating the treatment picture is that prescription
decisions are made by a variety of physicians: general practitioners and infectious
disease specialists - both of whom tend to be more comfortable with the iv and
oral drugs, and retinal specialists, who may be more comfortable with the CHIR
implant. The treatment decision thus may depend on which physician diagnoses
Vitrasert consists of a nonerodable polymer-based sustained
release package containing ganciclovir, and is surgically implanted in the posterior
of the eye. In clinical trials, median time to progression of disease was 216
However, surgical complications included retinal detachment, vitreous hemorrhage and a few cases of endophthalmitis (ocular inflammation). The other significant adverse event was loss of visual acuity following surgery, which resolved within two to four weeks. In addition, CMV is a systemic disease while Vitrasert is a local therapy, raising questions about whether patients using Vitrasert should receive systemic therapies as well.