Menlo Therapeutics has said its phase 2 trial of serlopitant in chronic itching (pruritus) is a bust, blaming the result on a high placebo response rate.
Shares in the US biotech closed down almost a third after the announcement, which indicated neurokinin-1 antagonist serlopitant had missed all the primary and secondary endpoints in the 233-patient study.
The reversal wiped out a steady series of gains for the stock since it announced a merger with Foamix Pharmaceuticals, despite Menlo’s insistence that the failure wouldn’t disrupt that deal, now expected to close around 9 March.
It also said the data has no read-through to its lead indication for serlopitant in pruritus associated with skin disease prurigo nodularis. Data from phase 3 trials in that indication is due in March or April of this year, and if positive could lead to a filing before year end, said the biopharma company.
The 10-week trial compared treatment with serlopitant versus placebo in 233 patients with self-reported chronic pruritus of unknown origin (CPUO), who experienced persistent itching for at least six months prior to enrolment.
At the end of the study period, 37.9% of patients in the serlopitant group achieved a four-point or greater improvement in the worst-itch numeric rating scale (WI-NRS) used to gauge symptoms, but that threshold was hit by 39/3% of the placebo group – around 10% higher than prior placebo results in trials.
“We conducted this trial in CPUO in the hope of offering the first-ever approved therapy for patients suffering from severe pruritus associated with this condition,” said Steve Basta, Menlo’s chief executive.
“The higher placebo response rate may be due to characteristics of the CPUO population, which is not well understood clinically,” he continued on a conference call, adding that he viewed this result as “an outlier” for serlopitant.
There’s no question that the trial result is a massive disappointment as well as a missed commercial opportunity for Menlo, given that it is estimated that approximately two million people may have CPUO – defined as itching lasting six weeks or longer – in the US alone.
Prurigo nodularis – a condition that causes lesions in the skin that are the cause of the intense itching suffered by patients – could be an easier win for the drug as there is a defined pathology in play, whilst CPUO could result from multiple causes. Menlo reported positive phase 2 data in that indication two years ago.
It’s not the first time that serlopitant has been undermined by a high placebo response rate in trials, however, as the drug previously missed the mark in atopic dermatitis – much like rival Vanda Therapeutics did with its rival NK1 drug tradipitant this week – as well as chronic cough.
Foamix CEO David Domzalski joined the conference to call to lend support, saying that the driver for the merger had always been serlopitant’s potential in prurigo nodularis.