Tuesday, May 8, 2018

FDA Cautious on Triglyceride-Lowering Antisense Drug WAYLIVRA

Today, the FDA released review material for the Advisory Committee Meeting on Volanesorsen (trade name WAYLIVRA) this Thursday.  WAYLIVRA has been developed for the lowering of serum triglyceride level in patients with a genetic form of severely elevated triglycerides, familial chylomicronemia syndrome (FCS).  Briefing Docs provide valuable insights as to the safety of drug candidates which are often glossed over by sponsor companies leading up to such regulatory events.

Echoes of KYNAMRO

The last time we had this opportunity in the phosphorothioate antisense space was in 2012 when the subject was the ApoB-lowering KYNAMRO.  Like KYNAMRO, WAYLIVRA is a second-generation 2’-MOE phosphorothioate-backbone oligonucleotide that was given at high doses in the registrational trials (200mg for KYNAMRO, 300mg for WAYLIVRA). 

It should therefore not come as a surprise that the safety and tolerability of WAYLIVRA was quite poor. In particular, not only did the at times drug-induced severe thrombocytopenia cause considerable bleeding concerns, the sponsor Akcea and parent company Ionis Pharmaceuticals have no idea about how to mitigate such risk.  Dose adjustments and increased platelet monitoring apparently did not change the thrombocytopenia risk substantially and apparently are still being made to this date without much rhyme or reason.   

In addition, there were the flu-like symptoms, liver enzyme elevations, renal tox, even a case of anaphylaxis causing around half of what should be highly motivated patients with FCS to drop out from the clinical studies.

This time it’s potent though

Fortunately, unlike KYNAMRO, WAYLIVRA has robust potency.  For those that managed to stay on the 300mg weekly dose, serum triglyceride lowering in excess of 70% was seen (reflecting ~90% target ApoCIII-lowering; cf. ~20% target-gene lowering with KYNAMRO).  Even the FDA had to acknowledge here that this is an unparalleled achievement.

But the positives end here already, with the FDA noting that in contrast to Akcea’s/Ionis’ claims there is no reliable reduction in measures of actual morbidity of FCS patients such as pancreatitis attacks, abdominal pain, and general well-being.  In fact, on most measures there was not even a numerical benefit favoring WAYLIVRA.  This, the FDA agrees, is also a function of the low number of patients available for such ultra-orphan disease studies.

The FDA admits that lowering of the biomarker serum triglyceride, even to much lesser extents than WAYLIVRA, has formed the basis for approving other drugs for hypertriglyceridemia-related disease.  In light of this, I expect WAYLIVRA to receive a favorable panel vote on Thursday on the condition that access to WAYLIVRA is strictly limited and safety tightly monitored (à REMS).  It apparently scares the FDA that while FCS has an estimated prevalence of 1 to 2 in a million, up to 1 in 600 have very high triglycerides resembling FCS.

Having said this, I am not quite clear why there should be different risk/benefit threshold with regard to the triglyceride-related morbidity for FCS and conditions resembling FCS as long as these other patients have exhausted options to treat the underlying causes for their particular hypertrigliceridemia.  As such, I believe the market potential estimates ought to be dramatically increased for WAYLIVRA.

WAYLIVRA competition

It is already clear, however, that WAYLIVRA will have a limited shelf-life.  Hot on its heels is a GalNAc-conjugated in-house competitor (ApoCIII-LRx) which has shown triglyceride lowering approaching that of WAYLIVRA, but at 5-10x lower dose levels, less frequent dosing and, crucially, with supposedly none of the worrisome safety issues of WAYLIVRA.  A phase III study of that compound is planned for 2019.  By that time, an RNAi GalNAc compound by Arrowhead should also be well in the clinic setting up ApoCIII-lowering to become a substantial market for oligonucleotide therapeutics by expanding the market well beyond the FCS population.   

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By Dirk Haussecker. All rights reserved.

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