Merck Serono initiates Ph II trial of cladribine

German-Swiss drugmaker Merck Serono has initiated a Phase II study to evaluate the safety, tolerability and efficacy of two dose regimens of its proprietary oral formulation of cladribine when added to the new formulation of Rebif (interferon beta-1a) in multiple sclerosis patients with active disease despite treatment with Rebif.

Oral cladribine is currently also being evaluated as a monotherapy in a fully-enrolled Phase III pivotal trial for first-line treatment of relapsing forms of MS. The new formulation of Rebif is under regulatory review by the European Medicines Agency (EMEA), the US Food and Drug Administration and other health care authorities. The firm believes the different mechanism of action and the oral intermittent administration of oral cladribine make it a potentially useful add-on therapy to Rebif.

The Phase II ONWARD study is a two-year, randomized, double-blind, placebo-controlled, international trial that will be conducted in 40 sites located across the USA and Europe, involving 260 Rebif-resistant MS patients. Study participants will be randomized in one of the three arms of the study to receive one of two different dose regimens of oral cladribine or matching placebo tablets.