Shares in US pharma company Rigel took a nosedive yesterday after an asthma drug in development at the company failed a phase II trial.
Shares in the company closed down a little over $3, the lowest level in its history and well short of its 52-week high of $10.95, after it reported that R343 did not meet any of its objectives in the study and would be discontinued as an allergic asthma treatment.
R343 was unable to show any improvement in lung function after eight weeks compared to placebo in the study, although it was safe and well-tolerated.
“This was not the result we expected based on the collection of data we had previously seen with R343 in this therapeutic area,” commented Rigel’s chief executive James Gower.
The disappointment is another blow to the US firm after AstraZeneca (AZ) decided in June not to press ahead with a filing for rheumatoid arthritis candidate fostamatinib (R788) after taking a look at clinical data on the drug. The fact that AZ also returned the rights to fostamatinib despite its own lacklustre pipeline does not bode well for the programme.
R343 is an inhaled Syk (spleen tyrosine kinase) inhibitor, in the same drug class as fostamatinib which is an orally bioavailable drug, and was at one point licensed to Pfizer which returned rights to Rigel in 2011.
Rigel now has to decide whether to press ahead with its own regulatory filing for fostamatinib based on the marginal efficacy seen in trials to date in patients who have failed to respond to treatment with disease-modifying anti-rheumatic drugs (DMARDs).
Beyond fostamatinib, the company has R333, a topical JAK3/Syk inhibitor in a phase II trial for the treatment of the chronic skin condition discoid lupus erythematosus (DLE) and R348, another JAK/Syk inhibitor in phase I testing as a treatment for dry eye.
It also has an inhaled JAK inhibitor called R256 in preclinical development with potential in asthma that was licensed to AZ in a $100m deal last year.
The company is sitting on cash reserves of around $250m as of the end of June and has been burning cash at a rate of around £25m a quarter.
The demise of R343 is not the first piece of evidence undermining the prospects for the Syk inhibitor class. For example, Biogen Idec and Portola Pharmaceuticals’ orally-active PRT2607 appears to be in development limbo after a phase I trial in rheumatoid arthritis was terminated. Biogen Idec licensed rights to the compound and other Syk inhibitors in a deal valued at up to $553.5m (including $45m upfront) in 2010.
Over the last couple of years momentum has been building behind other treatment approaches, particularly the JAK inhibitors such as Pfizer’s Xeljanz (tofacitinib) which is now rolling out in markets around the globe as a treatment for RA.