DGAP-News: ABIVAX / Key word(s): Study results ABIVAX: ABX464 shows excellent long-term efficacy data in Abivax's phase 2b maintenance Trial in ulcerative colitis 2021-10-18 / 18:00 The issuer is solely responsible for the content of this announcement.

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ABX464 shows excellent long-term efficacy data in Abivax's phase 2b maintenance Trial in ulcerative colitis . Impressive clinical remission in 58.4% (ITT) of 101 patients after 48 weeks of once-daily oral 50mgABX464, showing both maintained as well as further improved efficacy . Favorable safety and tolerability profile continues to support ABX464 chronic use potential . Launch of global phase 3 program with ABX464 in ulcerative colitis in preparation, with end-of-Phase-2 USFDA meeting in Q4 2021 and EMA Scientific Advice in early Q1 2022 . Abivax's late-breaking abstract presentation and Live Industry Symposium at UEG Week Virtual 2021 nowpublicly available

PARIS, France, October 18, 2021 - 6:00 pm (CEST) - Abivax SA (Euronext Paris: FR0012333284 - ABVX), a clinical-stage biotechnology company developing novel therapies that modulate the immune system to treat chronic inflammatory diseases, viral infections, and cancer, today reports new results from an extended set of patients in its ongoing open-label maintenance study, following the phase 2b induction study of once-daily oral 50mg ABX464 to treat ulcerative colitis (UC). These new data from the ongoing maintenance trial (data cut-off September 15, 2021) were presented during the late-breaking abstract presentation at UEG Week Virtual 2021 on October 4 by principal investigator Prof. Séverine Vermeire and are summarized in this release. These data emphasize ABX464's capacity to maintain and further improve patient-outcomes over time, as well as its continued favorable safety and tolerability.

Prof. Séverine Vermeire, M.D., Ph.D., Head of the IBD Center at the University Hospitals Leuven, Belgium, and principal investigator of the study, said: "Patients suffering from chronic inflammatory diseases, such as UC, often struggle to find a suitable treatment. Indeed, there is significant unmet medical need as a significant proportion of UC patients stop responding to currently available therapies within the first year of treatment, or do not respond at all. More than 80% of the patients in clinical remission at the end of induction were still in remission with a treatment of 50mg once daily oral ABX464 after the first year of maintenance treatment. In addition, almost 50% of the patients who were not in clinical remission after the induction study, achieved clinical remission during this first year of maintenance. ABX464 showed a persistent good safety and tolerability profile during the first year of treatment."

Prof. Hartmut J. Ehrlich, M.D., CEO of Abivax, said: "We are very pleased with the confirmation of the long-term efficacy of ABX464 for the treatment of ulcerative colitis. This trend was already observed in the phase 2a proof-of-concept study, in which 50% of the patients (ITT) were still in clinical remission after 3 years of treatment. These impressive results are now further strengthened by the first 101 patients who completed the one-year maintenance in phase 2b. Importantly, most published maintenance studies with other drugs only allowed patients who already showed a clinical response in the short-term induction study to enter into maintenance, thereby overestimating their long-term efficacy rate. In contrast, all patients had the possibility to continue their treatment in the ABX464 maintenance study, irrespective if they had a clinical response or not at the end of induction, thereby giving a chance even to the most severe cases. We are committed to rapidly bringing ABX464 into phase 3 testing, as we want to make this potentially transformative drug-candidate available as quickly as possible to patients suffering from ulcerative colitis."

ABX464 phase 2b clinical maintenance study in ulcerative colitis - 101 patients completed 48 weeks The new data from the phase 2b open-label extension study in UC, presented by Prof. Séverine Vermeire during the late-breaking abstract session at UEG Week Virtual 2021, included 101 patients who completed 48 weeks of chronic treatment with ABX464 as of September 15, 2021.

97.7% (217/222) of all patients who completed the phase 2b induction study, irrespective of treatments or treatment outcome during the induction phase, enrolled in the subsequent open-label maintenance study to evaluate the long-term safety and efficacy profile of ABX464 for up to two years. 


                        All patients       Patients with clinical response^[1]     Patients without clinical response 
                                                     after induction                        after induction 
At week 48          PP^[2] n= ITT^[3] n=      PP n=54            ITT n=63              PP n=34            ITT n=38 
                       88        101 
Clinical remission^   n=59       n=59       n=40 (74%)         n=40 (63.5%)          n=19 (55.9%)        n=19 (50%) 
[4], *                (67%)    (58.4%)

* Drop-outs (13 patients) were considered as treatment failures in the ITT analysis.

Among the subset of 101 patients for whom 1 year maintenance data is currently available (cut-off date: September 15, 2021), 28 had entered the maintenance study already in clinical remission: 23/28 (82.1%) of these patients stayed in clinical remission and only 5/28 patients (17.9%) lost clinical remission during this first year of maintenance.

Importantly, 36/73 patients (49.3%) who were not in clinical remission at the end of induction achieved a de novo clinical remission during the first year of maintenance.

Remarkably, the clinical remission rate for patients who did not show at least a clinical response at the end of the induction phase was 55.9% (PP) and 50% (ITT) after 48 weeks of treatment, demonstrating that long-term administration of ABX464 provided substantial clinical benefits also for these patients.

During the induction and the maintenance phases of the phase 2b study, ABX464 continued to show a good safety and tolerability profile, confirming the data already generated in over 850 patients and volunteers treated with ABX464 so far.

In May and September 2021, Abivax already announced the top-line and full results, respectively, of this randomized, placebo-controlled phase 2b trial of ABX464 in moderate to severe ulcerative colitis patients following induction treatment.

254 patients with moderate to severe active ulcerative colitis were enrolled in this phase 2b trial and randomized to three once-daily oral ABX464 treatment groups (25mg, 50mg and 100mg) or placebo. 50% of these patients had inadequate response, loss of response, or intolerance to biologics and/or JAK inhibitors treatments while the other 50% were refractory to conventional treatments. Endoscopies were read centrally and in a blinded fashion by independent reviewers. The baseline disease characteristics were well balanced across all ABX464 dose groups and the placebo group. Enrolled patients suffered from longstanding UC (with a mean duration of 7.4 to 8.8 years by treatment group) and 71.4% of the patients showed a severe disease profile (modified Mayo Score of 7 to 9 at screening).

Phase 2a ABX464 maintenance study in ulcerative colitis - 15 patients completed 3^rd year of treatment In addition to the phase 2b maintenance results, Abivax recently also reported efficacy data from its ongoing phase 2a maintenance study in UC.

15 out of the 22 patients who were initially enrolled into the phase 2a maintenance study completed the third year of treatment with 50mg once daily oral ABX464 as of June 29, 2021.

Among the 13 patients who had centrally read endoscopies at the completion of year 3, 11 patients (85%) were still in clinical remission, of which 7 patients (54%) had an endoscopic remission (endoscopic subscore=0) and 11 patients had an endoscopic remission or improvement (endoscopic subscore=0 or 1).

The long-term safety profile of chronic ABX464 administration continues to be favorable.^[5]

Launch of ABX464 global phase 3 clinical development program in ulcerative colitis Abivax is currently preparing the launch of its global phase 3 clinical program with ABX464 in about 1,400 patients with moderate to severe UC, and is already engaged in discussions with the relevant regulatory authorities. The End-of-Phase-2 meeting with the US regulatory agency (FDA) is scheduled for Q4 2021. Subject to positive feedback from FDA and the subsequent scientific advice from the European Medicines Agency (EMA), scheduled for early Q1 2022, Abivax intends to start the recruitment and inclusion of the first patients as quickly as possible.

Success of Abivax late-breaking abstract presentation and live symposium at UEG Week Virtual 2021 Abivax's late-breaking abstract on its ABX464 phase 2b clinical data in UC was accepted as an oral presentation for this year's UEG Week Virtual conference and was presented by Prof. Séverine Vermeire, M.D., Ph.D, the principal investigator of the study, on Monday, October 4.

In addition, Abivax hosted an Industry Symposium at UEG Week Virtual 2021 on "ABX464, a novel anti-inflammatory drug-candidate for the treatment of ulcerative colitis". Presentations were given by the internationally renowned key opinion leaders Prof. Bruce Sands, M.D., M.S. and Prof. William Sandborn, M.D.

The late-breaking abstract presentation and the replay of the Industry Symposium are now publicly available on the Abivax website at www.abivax.com/uegweek2021/

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October 18, 2021 12:00 ET (16:00 GMT)