Vertex slumps as FDA delays hepatitis C trial

US drug maker Vertex Pharmaceuticals (Nasdaq: VRTX) saw its shares drop 11% to $78 a share, in after-hours trading on Thursday (July 25), when the company said it has received notice from the US Food and Drug Administration that a partial clinical hold has been placed on the firm’s ongoing Phase II US study of the nucleotide analogue hepatitis C virus (HCV) polymerase inhibitor VX-135.

The partial clinical hold prevents evaluation of a 200mg dose of VX-135 in the US study following observation of reversible elevated liver enzymes in patients receiving 400mg of VX-135 in combination with ribavirin in a Phase II study in Europe. Evaluation of a 100mg dose of VX-135 in combination with ribavirin as part of the 12-week Phase II study in the USA is continuing as planned.

Vertex recently completed dosing of 100mg and 200mg of VX-135 in combination with ribavirin as part of the 12-week Phase II study in Europe, and both doses were well tolerated with no discontinuations. No serious adverse events have been reported and no liver or cardiac safety issues have been identified. Vertex also recently initiated dosing of 100mg and 200mg of VX-135 in combination with daclatasvir as part of a Phase 2 study in New Zealand.