PDL's Anti-Infection Agent For Bone Marrow Transplants Scores Well In Phase II
By Frances Bishopp
Staff Writer
Protein Design Labs Inc. (PDL) can at last report successful results for its product, Protovir human anti-cytomegalovirus (CMV) antibody, after it failed in past clinical trials. Whether the product has a future, however, is still up in the air.
Phase II clinical trial results of Protovir for the prevention of CMV infections in donor bone marrow transplantation demonstrated that patients who did not have a CMV infection prior to transplant and received grafts from CMV positive donors showed a statistically significant lower incidence of the primary endpoint, which was CMV infection, death or disease relapse, in the Protovir treatment group (24 percent) vs. the control group (70 percent) at 98 days post-transplant (p=0.003).
"Since we just unblinded, we have to look further at the data," Fred Kurland, vice president and chief financial officer of Protein Design Labs, told BioWorld Today. "We also have to look at the market potential of this product. This particular class of circumstance (recipient being negative, donor being positive) roughly represents about 20 percent of the patient population in a bone marrow transplant setting."
Kurland said PDL also will be determining if it's appropriate to consider solid organ transplants for the product.
A total of 179 cancer patients needing bone marrow transplants were enrolled in the randomized, double-blind study. Patients received up to seven doses of either placebo or 15 mg or 60 mg of Protovir. The first dose was administered one day prior to transplantation and subsequent doses were given every other week.
A smaller percentage of patients treated with the higher dose of Protovir (61 percent) reached the primary endpoint than did patients receiving lower doses of Protovir (72 percent) or placebo (72 percent), regardless of their prior CMV status.
The study showed Protovir treatment was well tolerated and did not cause an immune response.
In August 1996, PDL reported Protovir had failed in a Phase II/III trial which was assessing the antibody as a supplement to antiviral drugs. The study in CMV retinitis patients had enrolled 209 of 325 patients when it was stopped upon recommendation of an independent monitoring board, which reported the median time to progression of CMV retinitis was 65 days in the Protovir group and 66 days in the placebo group. Also reported was a higher mortality rate among the drug group, a difference seen only in patients with relapsed retinitis.
In September 1996, PDL stopped enrolling patients in a Phase II trial of Protovir for CMV retinitis, after the AIDS Clinical Trials Group, which was running the trial, recommended the use of higher doses.
"We are quite pleased with these results [Protovir in bone marrow transplantation] because we had theorized the reason we did not show efficacy in CMV retinitis is because we couldn't get enough drug through the eye-blood barrier. Bone marrow transplant is a different circumstance because the product is carried in the blood," Kurland said.
"If we were right about our theory as to why it might not have worked in CMV retinitis, that circumstance does not negate the potential efficacy of Protovir in a bone marrow transplant setting, where the CMV is in the bloodstream," he said.
Protovir was originally developed at Sandoz Pharma and Sandoz Pharmaceuticals Corp. (Novartis AG, of Basel Switzerland) and was in-licensed by PDL in 1993.
PDL has North American and Asian rights to develop and market Protovir and shares with Novartis certain copromotion and comarketing rights in North America and Asia.
Exclusive rights to therapeutic uses of Protovir in Europe and the rest of the world have been licensed to Boehringer Mannheim GmbH, of Mannheim, Germany.
PDL, as of March 31, 1997, had $163.9 million in cash on hand. PDL's stock (NASDAQ:PDLI) closed Wednesday at $26.875, down $0.50. *
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