FDA turns down 'national priority' drug from Disc Medicine

One of the beneficiaries of the FDA's national priority vouchers, Disc Medicine, has had its marketing application turned down by the regulator.

A complete response letter (CRL) was sent by the FDA for Disc's bitopertin for erythropoietic protoporphyria (EPP), which was among the first programmes to be awarded the controversial Commissioner's national priority voucher (CNPV) programme.

Bitopertin is an oral GlyT1 inhibitor designed to treat EPP, a form of inherited metabolic disorder caused by an enzyme deficiency, that leads to a buildup of protoporphyrin in cells and results in severe skin pain, burning, and itching on exposure to light.

In a statement, Disc said the FDA had acknowledged that the two phase 2 studies submitted to support its bitopertin filing – AURORA and BEACON – showed that the drug was able to reduce levels of a biomarker for protoporphyrin levels, PPIX. It had been seeking accelerated approval on the strength of that data, on the promise that its efficacy would be confirmed in later studies.

However, the agency has said it wants to see the results of an ongoing phase 3 trial, called APOLLO, before making a decision. According to Disc, it is not convinced about PPIX data because there is a lack of a strong correlation between the percentage reduction of the biomarker and clinical endpoints, including light tolerance and the rate of phototoxic reactions.

APOLLO is due to read before the end of this year, so the delay may not be very long, but the decision dashes Disc's hopes of approval and launch "in early 2026." On the plus side, if APOLLO does deliver a positive result, Disc reckons it will be able to go directly for a full, rather than conditional, approval.

"Upon completion of APOLLO, Disc would then file a response to the CRL and expect an updated FDA decision by mid-2027," said the company.

The CNPV programme was launched earlier this year and is designed to bring important new therapies to patients more quickly and plug gaps in the domestic supply of essential medicines, with FDA reviews in two months or less. However, questions have been raised about its legality and vulnerability to political influence.

The first medicine to be approved under the scheme was a US-manufactured version of the widely used antibiotic Augmentin XR (amoxicillin-clavulanate potassium).

"We are committed to delivering bitopertin to patients, knowing how critical this potentially disease-modifying therapy is to the EPP community," said Disc's chief executive, John Quisel.

"The CRL will delay the potential approval of bitopertin, but we have confidence in the ongoing APOLLO trial, for which we are seeing incredible enthusiasm from the EPP community," he added.