AnaptysBio plans phase 2b peanut allergy trial after taking positives from POC data

AnaptysBio has committed to moving peanut allergy drug ANB020 into a phase 2b trial after getting a look at data from a small proof-of-concept study. But the size of the trial and AnaptysBio’s analysis of the data leave scope for questions about the strength of the findings and their implications for the anti-IL-33 antibody.

Investigators enrolled 20 patients they classed as having moderate-to-severe peanut allergies and randomized them to receive a single dose of ANB020 or placebo on a three-to-one basis. Seven of the 15 patients in the treatment arm tolerated a 500mg cumulative dose of peanut protein 14 days after receiving ANB020. Mean tolerance at baseline was 229mg. In the placebo group, two of the five participants tolerated the 500mg dose at day 14. 

That amounts to an underwhelming response rate separation from placebo of 47% versus 40%. The results look decidedly better in AnaptysBio’s analysis, though. The San Diego-based biotech stripped two patients from the placebo group—both responders—and two from the treatment arm on the grounds they “exhibited mild symptoms at baseline.” 

Excluding the four patients from the analysis resulted in far more impressive findings, with 46% of patients in the treatment arm responding compared to 0% in the placebo group. Management thinks those figures, free from the confounding influence of the patients defined as having mild allergies, give a truer picture of the effect of ANB020 but it is yet to quell all doubts.

“The goal was to screen out mild patients by requiring previous history of anaphylaxis. However, it's now clear that past anaphylactic response is not a perfect predictor of current severity,” Jefferies analysts wrote after hearing management’s explanation of the analysis. “Adjudication of patients to mild versus moderate-severe categories was solely at discretion of blinded investigators who applied PRACTALL protocol which aligns with practice patterns of most U.S. allergists.”

AnaptysBio emerges from the POC trial with data that give it the confidence to move into a larger, multidose phase 2b. But the clinical and commercial prospects of ANB020 remain uncertain, even before the wildly-different patient populations used in AnaptysBio’s trial and those of rival drugs from Aimmune and DBV Technologies are factored into the analysis of the competitive landscape.

Shares in AnaptysBio rose 11% in after-hours trading.