PTC stung by FDA decision not to approve rare disease drug

It looks like PTC Therapeutics will have to carry out another clinical trial of its drug candidate for inherited neuromuscular disorder Friedreich's ataxia (FA) before the FDA will consider approval.

The US regulator has sent a complete response letter (CRL) to PTC, declining to approve the drug, called vatiquinone, because it said the main MOVE-FA study filed in support of the application had not shown conclusive efficacy.

The decision did not come entirely out of left field, and that may be why PTC's share price barely moved in response to the announcement.

PTC had moved ahead with a filing for the 15-LO inhibitor on the back of the MOVE-FA data, even though the study failed to meet its primary objective of improving symptoms of the disorder compared to placebo at 72 weeks.

The study looked at the efficacy of the drug on symptoms of FA affecting upper and lower limb coordination, swallowing, speech, and stability when standing. While it missed the main endpoint, PTC opted to file for approval regardless, based on data in a subgroup of patients who adhered to the drug throughout the study, as well as results on secondary outcome measures like fatigue levels.

"We are, of course, disappointed by the FDA's decision to not approve vatiquinone," said Matthew Klein, PTC's chief executive, who noted that the FDA is seeking another 'adequate and well-controlled' study.

"We believe the data collected to date demonstrate that vatiquinone could provide a safe and effective therapy for both children and adults living with Friedreich's ataxia," he added. "We plan to meet with the FDA to discuss potential steps to address the issues raised in the CRL."

The muted response to the FDA's decision among investors could stem in part from an acknowledgement that vatiquinone is considerably less important to the company's growth in the coming years than its new treatment for the rare disease phenylketonuria (PKU), Sephience (sepiapterin), which was approved in the EU in June and in the US last month and is heading for a decision in Japan before the end of the year.

Analysts at JPMorgan have modelled peak global sales of $1.2 billion for Sephience, with $750 million of that total coming from the US market, representing a big source of growth for PTC, which recorded sales of $179 million in the second quarter and is modelling full-year revenues of $650 to $800 million.