INF904 Shows Strong Phase 2a Results in HS and CSU, With No Safety Signals

On November 10, 2025, InflaRx reported positive phase 2a preliminary results showing that its oral C5aR inhibitor INF904 produced rapid, meaningful clinical improvements in both hidradenitis suppurativa (HS) and chronic spontaneous urticaria (CSU) with no safety signals.1 These findings prompt plans to advance the therapy into phase 2b development.

“Results from our Phase 2a study indicate INF904’s positive safety profile to date and show promising signals of clinical benefit…” said Camilla Chong, MD, chief medical officer of InflaRx, in a statement.1 “We are particularly proud to have advanced this study to this stage in less than a year from study start, which was made possible thanks to the dedication of our clinical team and the excellent collaboration with investigators and their patients.”

INF904, an oral small-molecule C5aR1 inhibitor, has previously demonstrated anti-inflammatory activity, strong safety, minimal CYP3A4/5 interaction, and sustained ≥90% C5a blockade in first-in-human studies. InflaRx assessed the safety and the pharmacokinetics/pharmacodynamics profile of INF904 across 31 patients with HS and 31 with CSU in an 8-week multicenter, open-label trial. Efficacy served as an exploratory endpoint.

Investigators evaluated multiple INF904 dosing regimens (60 mg, 90 mg, and 120 mg) over 4 weeks of treatment, with an additional 4-week follow-up period where patients are not dosed with INF904. The study is ongoing, and investigators are working to complete the 4-week post-treatment observation period.

“As we move toward initiating phase 2b in HS and broadening the INF904 clinical program in CSU and beyond, we look forward to further validating INF904’s differentiated profile and advancing its development for patients in need,” said Niels C. Riedemann, chief executive officer and founder of InflaRx.1

Data on INF904 for Hidradenitis Suppurativa

InflaRx reported INF904 efficacy data from 29 patients with HS across all 3 dosing arms who completed 4 weeks of treatment: 10 on 60 mg, 11 on 90 mg, and 8 on 120 mg.1 The study also has additional data from 25 patients who had completed the subsequent 4-week follow-up observation period.

HS endpoints included the reduction in d combined abscesses + nodules (AN) and draining tunnel (dT) counts, achievement of hidradenitis suppurativa clinical response (HiSCR), pain reduction (Numeric Rating Scale 30 (NRS30)), and improvement in the Dermatology Life Quality Index (DLQI). INF904 led to rapid, meaningful improvements in these endpoints at week 1, with continued improvement over the 4-week treatment period. All doses demonstrated positive clinical activity, with the 120 mg dose appearing to be the most effective.

“These data in hidradenitis suppurativa (HS) are encouraging, demonstrating the potential for INF904 to rapidly and substantially reduce total inflammatory burden (TIB) - abscesses, nodules, and draining tunnels,” said John Ingram, clinical professor & consultant dermatologist at Cardiff University and specialty lead for dermatology, health and care research Wales, in a statement.1 “These findings suggest INF904 could meaningfully lessen the burden faced by HS patients, many of whom continue to suffer despite the relatively small set of approved therapies currently available.”

Data from the 25 patients who completed the 4-week observation period showed that HiSCR responses continued to improve even 4 weeks after treatment ended. PK results from week 8 indicate that INF904 levels remain sufficient to provide C5aR-blocking potential 4 weeks after discontinuation. Supporting this, an additional study found that INF904 maintains > 90% blocking of C5a-induced neutrophil activation at disease-relevant C5a levels 24 hours after dosing across the 30–240 mg range.2

Safety data was reported in 33 patients with HS. The study did not detect safety concerns or serious adverse events (SAEs).1 The study reported 3 adverse events in 2 patients that were considered “possibly-to-likely related to drug” but were mild in nature.

“Given the pressing need for novel mechanisms of action, and INF904’s emerging clinical profile as a well-tolerated and potentially effective oral therapy, I am optimistic about its advancement into later-stage development and its potential to address an important unmet need in HS,” Ingram said.

Data on INF904 for CSU

The study reported efficacy data on INF904 in 30 patients with CSU (14 on 60 mg and 16 on 120 mg). The study also had additional data from 23 patients who completed the observation period. Endpoints included change from baseline in UAS7, UCT7, and responder rate analyses.

Reported UAS7 improvements were greatest in the 60-mg cohort (-13.7 points at week 4), exceeding historical placebo responses and falling within the range of approved CSU therapies. Among patients with severe CSU at baseline (n = 23), the 60-mg dose reduced UAS7 by 15.4 points, and in those with angioedema (n = 3), by 18.7 points. INF904 also appeared similarly effective in patients with high (n = 22) and low (n = 6) baseline IgE.

In the 23 CSU patients who completed a 4-week off-drug follow-up, clinical benefit persisted, with the 60-mg group showing a mean UAS7 reduction of 16.7 points.

Safety data from 33 patients showed no concerns: no SAEs were reported, and only one mild, possibly drug-related adverse event occurred.

“The Phase 2a data for INF904 in chronic spontaneous urticaria (CSU) are encouraging, indicating clinical activity and safety,” said Martin Metz, MD, professor of dermatology and deputy director of the Institute of Allergology | Charité at Universitätsmedizin, in Germany, in a statement. “…by inhibiting the C5a receptor, INF904 appears to be acting on the inflammation environment underlying urticaria, which may further benefit from continued dosing. Given the unmet need in CSU, and the potential for INF904 as an effective and safe oral agent to benefit a significant number of patients, further exploration in CSU is clearly warranted.”

References

1. 11-2025-InflaRx Reports Positive Phase 2a Data for INF904 in Hidradenitis Suppurativa (HS) and Chronic Spontaneous Urticaria (CSU). Inflarx.de. Published 2025. Accessed December 1, 2025. https://www.inflarx.de/Home/Investors/Press-Releases/11-2025-InflaRx-Reports-Positive-Phase-2a-Data-for-INF904-in-Hidradenitis-Suppurativa--HS--and-Chronic-Spontaneous-Urticaria--CSU-.html

2. Press Release. Inflarx.de. Published 2023. Accessed December 1, 2025. https://www.inflarx.de/Home/Investors/Press-Releases/Press-Release~2023-09-InflaRx-Announces-Positive-Topline-Results-from-the-Single-Ascending-Dose--SAD--Phase-I-Study-with-C5aR-Inhibitor-INF904~.html