Idera Pharmaceuticals' (IDRA) stock market rollercoaster ride left it partially recovered from its 25% plunge just over a week ago upon FDA approval of a competing product developed by Celgene (CELG). Idera's plaque psoriasis candidate, IMO-8400, gave good results for safety and efficacy in a phase 2 trial, but the stock remains at half mast, as investors are unconvinced by Idera's story in a marketplace crowded with psoriasis options.
Phase 2 good but not great
Idera ran its double-blind, placebo-controlled phase 2 trial in 32 patients with moderate-to-severe plaque psoriasis with a primary goal of showing safety and tolerability of IMO-8400 with 12 weeks of treatment. The secondary endpoint was efficacy as measured by Psoriasis Area and Severity Index (PASI).
All three dose levels of the drug were safe and well-tolerated, which is an absolute necessity to be really competitive in the psoriasis market. Currently available therapies include steroids, topical retinoids, vitamin D derivatives, immune suppressants, and TNF-α inhibitors like Amgen and Pfizer's Enbrel. Those therapies carry some significant risks, however, such as kidney failure for the retinoids and cancer for some of the TNF-α inhibitors. A competitive opportunity exists, then, for a therapy that is shown to be safer. By that standard, IMO-8400 so far passes with flying colors.
However, the PASI scores, while good, are not all that might have been hoped for. PASI is a composite of the redness, thickness, and scaling of psoriasis over several regions of the body. In the trial, nine out of 20 patients, or 45%, achieved a 50% reduction (PASI-50), compared to only one out of seven patients in the placebo group. Only four patients, or 20%, achieved a stricter standard, 75% PASI reduction (PASI-75).
Additional clinical results in an expansion cohort of 12 patients based in the Netherlands are due in a couple of months.
No apples to apples comparison
While that certainly indicates some efficacy (in, admittedly, a small sample), it falls short of higher hopes based on an earlier study that handed in PASI improvements in the 35% to 90% range, and it appears weak compared to Celgene's results for newly approved Otezla, which achieved a 33% PASI-75 score with 16 weeks of treatment in the ESTEEM 1 study and 29% in the ESTEEM 2 study.
Although it would have been great for Idera to knock it out of the park with a really high PASI-75 score, ultimately the important takeaway for efficacy is that in this small trial the drug appeared effective and is worth further study. For a number of reasons, numbers are only roughly comparable from one clinical trial to the next and one drug to the next, so lacking a direct, head-to-head trial, it's hard to say which is superior, the drug with 20% PASI-75 after 12 weeks of treatment (IMO-8400) or the drug with a 29%-33% PASI-75 score after 16 weeks of treatment. This is especially true given the small sample size for the IMO-8400 trial.
A proof of concept for TLR antagonists
A successful psoriasis drug could have potential for a billion or more in annual sales, based on Celgene's guidance of up to $2 billion for Otezla. But Idera views its trial results as more than a test of the drug's potential in plaque psoriasis. IMO-8400 is Idera's lead candidate in the class of Toll-like receptor (TLR) 7, 8, and 9 antagonists. In addition to psoriasis, Idera is planning to develop IMO-8400 in genetically defined forms of B-cell lymphoma and orphan autoimmune diseases.
The company views the recently completed phase 2 trial as a proof-of-concept for TLR antagonists in autoimmune disease, and as such it may herald more successful drug candidates in more indications in the future. So the trial success suggests that IMO-8400 might not only be a significant player in the plaque psoriasis market, but a first-in-class therapy in cancer and orphan disease if it can continue to perform in clinical trials.
