Upcoming events – catalysts approach for Catalyst and Oxurion

Welcome to your weekly digest of approaching regulatory and clinical and readouts. Catalyst Pharmaceuticals has had a rough time of late following the launch of a cut-price rival to its rare disease therapy Firdapse, but it could soon get a boost from upcoming readouts in new indications. 

Catalyst expects data from two phase III trials of Firdapse in the second half of this year, one in congenital myasthenic syndromes and the other in Musk-antibody positive myasthenia gravis.

The group will hope to add these uses to Firdapse’s label; the drug got the US FDA nod in November for adults with Lambert-Eaton myasthenic syndrome (LEMS).

The populations involved are small: LEMS affects around 3,000 US patients, while there are 1,000-1,500 with congenital myasthenic syndromes and 3,000-4,800 with Musk-positive myasthenia gravis, Catalyst estimates.

Still, myasthenia gravis, in particular, could be a valuable indication: EvaluatePharma sellside consensus sees 2024 sales in this use of $191m, not far off the $203m forecast in LEMS.

Firdapse needs to show an improvement in the myasthenia gravis activities of daily living scale at day 10 versus placebo in the 60-patient phase III trial. But competition will be fierce in myasthenia gravis, a disease that Alexion’s Soliris is set to dominate.

In LEMS Catalyst made the most of having the only FDA-approved drug – at least until Jacobus Pharmaceuticals got the FDA go-ahead for Ruzurgi in May, and then undercut Firdapse’s $375,000 per year price.

The two companies already had a history, with Firdapse’s approval effectively stopping Jacobus giving Ruzurgi away for free under its compassionate-use programme. Firdapse is indicated for adult LEMS and Ruzurgi for children, but Catalyst fears off-label use of Ruzurgi in adults, and is suing the FDA over its decision to greenlight Jacobus’s drug.

Catalyst was roundly criticised for the cost of Firdapse in LEMS. If the group can get a result in myasthenia gravis it could meet its match in Alexion, the orphan drug pricing master.

Oxurion eyes success

After changing its name from Thrombogenics last September Oxurion will also be hoping to change its fortunes with positive readouts from a string of clinical trials between now and the end of the year.

The group has already scored a hit with THR-149 in diabetic macular oedema (DMO). Next up are phase II data from the 70-patient combination trial of its lead pipeline project, THR-317, again in DMO. The study will see THR-317 plus Roche’s Lucentis go up against Lucentis plus placebo.

If June’s results from a phase I/II trial of THR-317 as a monotherapy are anything to go by investors should be encouraged. The trial showed a dose-escalation effect between 4mg and 8mg, and 30% of patients taking 8mg, who had never received anti-VEGF treatment, achieved a 10-letter vision gain and 10% showed a 15-letter vision gain at 90 days.

Theoretically combining THR-317 with Lucentis should further improve efficacy. But Oxurion is using a new mechanism of action, placental growth factor, which could explain why so far few analyst have put any numbers on future sales of THR-317.

In addition, Oxurion should arguably be combining its project with Regeneron and Bayer's Eylea, which has shown benefits over Lucentis in DMO. Still, other efforts to best Eylea have fallen flat.

Even if THR-317 is successful, it could end up entering the market at around the same time as Lucentis and Eylea are set to lose patent protection.