Upcoming events: first look at Dificid in new patient population

Analysis

Welcome to your weekly digest of approaching regulatory and clinical readouts. An interim analysis is expected in the third quarter from a trial of Optimer’s antibiotic Dificid to prevent Clostridium difficile-associated diarrhoea (CDAD) in bone marrow transplant patients. With the study's adaptive design the data safety monitoring board will determine whether the sample size needs adjusting to detect a treatment effect.

Dificid sales in CDAD have been lacklustre owing to the increased reluctance of hospitals and pharmacies to pay for expensive novel antibiotics. Cubist Pharmaceuticals, which had been co-promoting Dificid since its launch in 2011, recently agred to acquire Optimer and negotiated sales milestones as part of the deal; questions remain over whether this new patient population can revive flagging forecasts.

Adaptive design

This latest phase IIIb trial called Deflect-1 aims to enrol 340 patients undergoing bone marrow transplantation. Treatment will be 200mg of Dificid daily for 30 days against placebo. The primary endpoint is the occurrence of CDAD from the first dose to the end of the 30-day follow-up period.

To achieve the endpoint Dificid needs to provide a 60% improvement over placebo in the incidence of CDAD from baseline. Leerink Swann analysts note that the expected placebo incidence of CDAD should be in the 10-25% range. 

The blinded interim analysis will be conducted after 170 patients have completed treatment and follow-up. With the adaptive design the DSMB may increase, decrease or maintain the total enrolment target. Increasing enrolment might suggest a weaker-than-expected response to Dificid, while decreasing it could be taken as a positive. Full data from the trial are expected in the second half of next year.

New patients

Optimer says 30% of patients undergoing bone marrow transplantation will develop CDAD because their weakened immune systems and use of prophylactic antibiotics make them more susceptible. Leerink Swann analysts estimate that prophylaxis for bone marrow transplants could amount to $300m in 2020 peak sales.

Dificid is on the market in the US and Europe for the treatment of CDAD in adults. Last year it had $62m in sales, with 2018 sales forecast to reach $291m, according to EvaluatePharma. Despite the high demand for novel antibiotics, sales have been languishing mainly because of the drug's high price and generic competition. Analysts have trimmed forecasts since the launch.

After two years of co-promoting Dificid, in July Cubist agreed to buy Optimer for $10.75 per share with another $5 per share on the table based on certain sales milestones. That values the deal at $535m or $801m at maximum (Cubist right to inject caution into much-needed acquisition spree, July 31, 2013). Cubist, meanwhile, has its own CDAD candidate, surotomycin (CB-315), in phase III, with data expected in 2014 or 2015.

While Optimer hopes that bone marrow transplantation will help drive Dificid sales, there is increased scepticism over its broader uptake and all eyes will be on its ability to sell in this patient population.

Study Trial ID
Deflect-1 NCT01691248

All information is sourced to analyst notes and the EvaluatePharma Calendar of Events tool.

To contact the writer of this story email Joanne Fagg in London at joannef@epvantage.com or follow @JoEPVantage on Twitter

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