PDL Share Price Plummets As Trial Disappoints

Protein Design Labs of Mountain View, California, experienced a set- back at the end of last month after it was forced to halt one of three ongoing trials of its anticytomegalovirus antibody, Protovir (MSL 109), as a supplemental treatment for CMV retinitis in patients with newly-diagnosed or relapsed disease. The Californian company cited lack of evidence of efficacy as the reason for the discontinuation.

The decision to halt the Phase II/III trial was made by the Studies of the Ocular Complications of AIDS (SOCA) group, which is supported by the National Eye Institute in the USA. An interim analysis, conducted after 209 of the target of 325 patients had been enrolled, revealed that the median time to progression was 65 days in the Protovir group and 66 days in the placebo group.

Excess Mortality Seen In Treated Group Of greater concern was the observation that there was a higher mortality rate in the antibody-treated group. The SOCA investigators noted that this excess mortality was only observed in the relapsed retinitis group (60% of those enrolled) and not in those with newly-diagnosed disease. "The meaning of this difference is unclear," said SOCA, adding that "there was a lower-than-expected rate of mortality in relapsed patients assigned to placebo.