Nov 18 (Reuters) - Early data from a small trial of Merck &Co Inc's experimental immunotherapy cancer drug, knownas MK-3475, show that about half of advanced melanoma patientstreated with the highest dose of the drug experienced tumorshrinkage.
Updated results from the early-stage trial are set to bepresented on Monday at the International Congress of the Societyfor Melanoma Research in Philadelphia.
The antibody drug is part of a new class of compoundsdesigned to block the activity of a receptor on immune cellscalled programmed death 1, or PD-1. The aim of the drugs is tospur the body's own immune system to attack cancer cells.
Merck said results from 135 patients whose melanoma hadstopped responding to earlier rounds of treatment showed that 41percent had tumor shrinkage - the rate was 51 percent in thehigh-dose group, and 40 percent for lowest-dose group.
The company estimated overall survival at a year oftreatment at 81 percent, but said the trial had not yet reachedeither a median duration of response or median overall survival.
Serious side effects seen in the trial included fatigue,rash, increased liver enzymes and renal failure.
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