DGAP-News: ABIVAX / Key word(s): Study results 
Abivax reports excellent efficacy and safety of ABX464 in phase 2b clinical trial in ulcerative colitis and plans to 
proceed to phase 3 
2021-05-24 / 18:30 
The issuer is solely responsible for the content of this announcement. 
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Abivax reports excellent efficacy and safety of ABX464 in phase 2b clinical trial in ulcerative colitis 
and plans to proceed to phase 3 
  . Primary endpoint (statistically significant reduction of Modified Mayo Score^[1]) was met with once-daily ABX464 
    (25mg, 50mg, 100mg) at week 8 in these 254 patients randomized, double-blind and placebo-controlled clinical trial 
    (p<0.05, intent-to-treat population [ITT]) 
  . Key secondary endpoints, including endoscopic improvement, clinical remission, clinical response and the reduction 
    of fecal calprotectin showed significant difference in patients dosed with ABX464 compared to placebo 
  . ABX464 also showed rapid efficacy in patients who were previously exposed to biologics and/or JAK inhibitors 
    treatment 
  . ABX464 was safe and well tolerated 
  . Preliminary data from 51 patients treated with 50mg ABX464 in the open-label maintenance study showed increased and 
    durable clinical remission and endoscopic improvement after 48 weeks^[2] 
  . Abivax to host webcast on Tuesday May 25, 2021 at 6 pm CEST (12 pm EST, 9 am PST), with participation of Prof. 
    Bruce Sands, M.D., M.S. 
PARIS, France, May 24, 2021 - 6:30 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, announces positive phase 2b clinical induction and preliminary maintenance 
study results. 254 patients with moderate to severe ulcerative colitis (UC) were treated with ABX464, a small molecule 
for once-daily administration with a first-in-class mechanism of action. 
The top-line data showed significant clinical efficacy in the overall patient population on primary and key secondary 
endpoints and a good safety profile of ABX464 during 8 weeks of induction treatment. Importantly, the overall drop-out 
rate of patients in the study was only 9%, which is remarkable in view of the Covid-19 situation. 
Furthermore, after 48 weeks of open-label maintenance treatment with ABX464, preliminary data from the first 51 
patients showed further increased and durable clinical and endoscopic efficacy. 
The phase 3 clinical program with ABX464 in UC is expected to start by year end.^[3] 
Abivax's clinical trial steering committee (Prof. Séverine Vermeire, Prof. William Sandborn and Prof. Bruce Sands) was 
convened on May 22, 2021 and reviewed and endorsed the phase 2b induction and maintenance top-line results and the 
corresponding conclusions. 
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: "I am very pleased with the outcome of this clinical trial, as it confirms and extends 
the results from the previous phase 2a study. Clearly, this promising drug-candidate needs to be taken into phase 3 as 
quickly as possible, as the medical need for patients suffering from moderate to severe ulcerative colitis is very high 
and new safe and effective treatments with innovative modes of action are urgently needed. I am looking forward to 
further support the planned phase 3 ulcerative colitis program as principal investigator." 
Prof. Bruce Sands, M.D., M.S., the Dr. Burrill B. Crohn Professor of Medicine at the Icahn School of Medicine at Mount 
Sinai, New York City, NY, added^[4]: "The ABX464 phase 2b induction and preliminary maintenance results are very 
compelling. I am especially impressed by the efficacy in severe patients who previously failed biologic and/or JAK 
inhibitors treatment and by the durable and increasing efficacy during maintenance treatment. Ulcerative colitis is a 
chronic disease and patients need long-term effective treatments, as many of them do not respond or stop responding to 
currently available drugs. Beyond its efficacy, safety and differentiated mode of action, ABX464 offers a once-daily 
easy oral administration." 
Prof. Hartmut J. Ehrlich, M.D., CEO of Abivax, said: "The phase 2b results demonstrate the potential of ABX464 to 
become a gamechanger for the treatment of ulcerative colitis patients in need of new therapeutic management options. 
Interestingly, the lowest dose of 25mg was effective across the entire study population, including patients refractory 
to biologics and JAK inhibitors, with a safety profile that is very similar to the placebo group. Based on these data, 
we are now moving forward as quickly as possible with our phase 3 plan in ulcerative colitis as well as phase 2b/3 in 
Crohn's disease to bring ABX464 to the many patients suffering from inflammatory bowel disease." 
Philippe Pouletty, M.D., Chairman of the Board of Abivax, commented: "With these excellent results, Abivax enters a new 
and exciting execution phase towards potential market approval of ABX464 for a major unmet medical need." 
ABX464 phase 2b induction study confirmed short-term efficacy in patients refractory to conventional treatments as well 
as patients previously exposed to biological and/or JAK inhibitor treatments and demonstrated a good safety profile 
The randomized, double-blind and placebo-controlled phase 2b induction study was conducted at 130 study sites in 15 
European countries, Canada and the US. It had three once-daily oral ABX464 treatment groups (25mg, 50mg and 100mg) and 
one placebo group. 254 patients with moderate to severe active ulcerative colitis were enrolled into the trial. 50% of 
these patients had inadequate response, loss of response, or intolerance to tumor necrosis factor alpha (TNF-?) 
inhibitors, vedolizumab, other biologics and/or JAK inhibitors treatments while the other 50% were refractory to 
conventional treatments. Endoscopies were read centrally and blinded by independent reviewers. Electronic patient 
diaries were used to promote the reliability of the collection of stool frequency, rectal bleedings and other patient 
reported outcomes. 
Gender, clinical, biological and endoscopic parameters were well distributed across placebo and treatment groups at 
enrollment time. The primary endpoint, i.e. the reduction of the modified Mayo Score from baseline after 8 weeks of 
treatment was statistically significant for all active treatment groups. 
 
               Week 8 top-line results                    Placebo          25mg             50mg            100mg 
             (ITT^[5]population / N= 252) 
                                                   Primary Endpoint 
Modified Mayo Score                   All patients         -1.9           -3.1 *           -3.2 *           -2.9 * 
Mean change from baseline             Bio exposed          -1.0           -2.8 *           -2.9 *           -2.8* 
*p-values of <0.05 versus placebo for all dose groups (ANCOVA) 
                        Key Secondary Endpoints (not powered to show statistical significance) 
Endoscopic Improvement ^[6]?          All patients       8 (13.6%)     20 (34.5%) *     21 (39.6%) *     24 (44.4%) * 
                                      Bio exposed        1 (2.9%)      8 (28.6%) *      7 (30.4%) *      8 (26.6%) * 
*p-values of <0.05 versus placebo for all dose groups using a likelihood ratio chi-square test 
Clinical Remission ^[7]?              All patients       8 (12.5%)     17 (27.9%) *      11 (17.5%)       16 (25.0%) 
                                      Bio exposed        1 (3.2%)      6 (20.0%) *        2 (6.7%)       6 (18.8%) * 
*p-values of <0.05 versus placebo using a likelihood ratio chi-square test but not according to the predefined 
Mantel-Haenszel Chi Square test (p<0.1) 
Clinical Response ^[8]?               All patients      23 (35.9%)     40 (65.6%) *     38 (60.3%) *     35 (54.7%) * 
                                      Bio exposed        5 (16.1%)     17 (56.6%) *     13 (43.3%) *     15 (46.8%) * 
*p-values of <0.05 versus placebo using a likelihood ratio chi-square test 
Fecal Calprotectin (µg/g)             All patients        -1027.7       -2192.8 **       -2316.8 **       -2280.9 ** 
Mean change from baseline 
**p-values of <0.01 versus placebo (MMRM)

Further and final results including pharmacokinetics, histology and miR-124 expression data will be available in due time.

ABX464 was shown to be effective in patients refractory to conventional treatments and, importantly, also in patients with inadequate response, loss of response, or intolerance to biologics and/or JAK inhibitors.

ABX464 was well tolerated at all dose levels during the induction phase as well as the maintenance treatment. Similarly low rates of infections were observed in the active treatment groups compared to placebo. No deaths or malignancies were reported in the study. In the ABX464 groups, serious adverse events (SAEs) occurred in 1.6% (25mg), 6.3% (50mg) and 6.2% (100mg) of patients and in 6.2% of patients in the placebo group. These safety data are in line with what has been observed in more than 650 healthy volunteers and patients who have so far been treated in other clinical trials with ABX464 across different indications.

Preliminary phase 2b maintenance study results show the potential of ABX464 as an efficacious chronic treatment with a good safety profile

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May 24, 2021 12:30 ET (16:30 GMT)