On December 7, 2022, Prometheus Biosciences, Inc. (“Prometheus” or the “Company”) reported results from its ARTEMIS-UC Phase 2 and APOLLO-CD Phase 2a studies of PRA023 demonstrating strong efficacy and favorable safety results in both studies. Based on the totality of the data in these two studies, Prometheus intends to advance PRA023 into Phase 3 studies for ulcerative colitis (“UC”) and Crohn’s disease (“CD”) in 2023. The Company will host a call today, December 7, 2022, at 8:30 am Eastern Time, to discuss the data results. A copy of the presentation that will be referenced during the conference call is filed as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein.
Topline Results from the ARTEMIS-UC Phase 2 Study
Prometheus’ Phase 2 ARTEMIS-UC clinical trial was a 12-week, double-blind, placebo-controlled, randomized study to evaluate the efficacy and safety of PRA023 in patients with moderately to severely active UC who have failed conventional or advanced therapy. PRA023 met the primary and all ranked secondary endpoints including clinical, endoscopic, histologic, and patient-reported outcome measures in the initial cohort (“Cohort 1”) of the trial. All 68 of the 68 PRA023-treated patients completed the Cohort 1 study, compared to 60 of the 67 patients in the placebo group. The topline results for the key endpoints were as follows:
| | • | | 26.5% of patients on PRA023 reached the primary endpoint of clinical remission (per modified Mayo Score), compared to 1.5% on placebo, for a placebo-adjusted clinical remission rate of 25.0% on the primary endpoint (p<0.0001); |
| | • | | 36.8% of patients on PRA023 reached the secondary endpoint of endoscopic improvement (Mayo endoscopy subscore of ≤ 1), compared to 6.0% on placebo, for a placebo-adjusted endoscopic improvement rate of 30.8% on the secondary endpoint (p<0.0001); and |
| | • | | All secondary endpoints met with statistical significance. |
PRA023 was well tolerated in Cohort 1, with no treatment-emergent serious adverse events (“SAEs”), adverse events (“AEs”) leading to discontinuation, severe AEs, opportunistic infections or infusion reactions reported in the PRA023 treatment group. The only AE that occurred in more than two patients and at a higher frequency in the PRA023 group compared to placebo was COVID-19 (5 out of 68 [7.4%] and 3 out of 67 patients [4.5%], respectively).
Based upon confidence in its precision approach and speed to market, the Company conducted an interim companion diagnostic (“CDx”) analysis of Cohort 1 to evaluate the effectiveness of the CDx candidate in ARTEMIS-UC. Although from limited patient numbers, data from the subset of patients who tested positive on the CDx in Cohort 1 (N=32) demonstrated a placebo-adjusted clinical remission rate of 37.5%, compared with the placebo-adjusted remission rate of 25.0% for all-comers. The expansion cohort (“Cohort 2”), which is statistically powered to further assess the treatment effect of PRA023 in CDx+ patients will continue to enroll, and the Company expects results in the second quarter of 2023.
Results from the APOLLO-CD Phase 2a Study
Prometheus’ Phase 2a APOLLO-CD clinical trial was a 12-week open-label study that enrolled 55 patients with moderate-to-severely active CD with endoscopically active disease who had failed conventional or biologic therapy. The study enrolled a highly refractory patient population with 70.9% of patients previously treated with at least one biologic therapy and 52.7% treated with two or more biologic therapies. The results on the key endpoints were as follows:
| | • | | 26.0% of patients on PRA023 achieved endoscopic response (p=0.002 compared to 12% prespecified historical placebo rate); and |
| | • | | 49.1% of patients on PRA023 achieved clinical remission (p<0.001 compared to 16% prespecified historical placebo rate). |
