Partial hold for Vertex's HCV compound, VX-135

Vertex Pharmaceuticals Inc. (NASDAQ:VRTX) said late Thursday that FDA placed a partial clinical hold on a U.S. Phase II trial evaluating oral VX-135 plus ribavirin in treatment-naïve patients with HCV genotype 1 infection. The hold is a result of data from a European Phase II trial showing that patients receiving 400 mg VX-135 plus ribavirin had reversible elevated liver enzymes. Vertex said it plans to submit additional clinical, preclinical and pharmacokinetic data from ongoing VX-135 studies to FDA in 4Q13.

The hold prevents Vertex from evaluating a 200 mg dose of VX-135 in the U.S. trial, though the company is continuing to dose patients in the trial's 100 mg arm. Data from that arm are expected this half. Vertex has exclusive, worldwide rights to VX-135, a nucleotide HCV NS5B polymerase inhibitor, from Alios BioPharma Inc. (South San Francisco, Calif.). ...