An experimental drug being developed by Shire to treat cytomegalovirus (CMV) infection has been given a boost in the US with a ‘Breakthrough Therapy Designation’.

The decision places Maribavir on a potentially faster regulatory pathway, as the conditions of a breakthrough status include intensive guidance on its development programme and eligibility - depending on supporting clinical data - for rolling and priority review of the marketing application.

CMV is a beta herpes virus that can cause challenging and potentially fatal complications in patients with compromised immunity, including organ or stem cell transplant recipients.

According to Shire, existing antiviral therapies can be used to treat CMV, “but their use may be limited by side effects and/or drug resistance”.

Maribavir is an investigational agent in a class of drugs called benzimidazole ribosides. By inhibiting the CMV UL97 protein kinase, the drug potentially affects several critical processes in CMV replication including viral DNA synthesis, viral gene expression, encapsidation and egress of mature capsids from the nucleus.

Highlighting the drug’s potential, the firm said data from one Phase II study showed that 67 percent of patients treated with varying doses of Maribavir for up to 24 weeks had no detectable levels of the virus in their blood plasma within six weeks of starting treatment.

“Maribavir has the potential to address critical medical needs for transplant patients who are refractory or resistant to currently available antiviral therapies, and I’m proud of the innovation and hard work that made this Breakthrough Designation Therapy milestone a reality,” said Andreas Busch, global head of R&D, Shire.