Belenos Biosciences has reported positive topline results from a Phase 2 study of BEL512, its investigational long-acting bispecific antibody targeting thymic stromal lymphopoietin and interleukin-13, in adults with inadequately controlled chronic rhinosinusitis with nasal polyps. The company said the 120-patient study met its primary endpoint and all disclosed secondary endpoints at Week 24, moving BEL512 toward an ex-China Phase 3 programme planned for the first half of 2027.
The result gives Belenos its clearest clinical validation yet for a strategy built around simultaneously inhibiting an upstream driver of type 2 inflammation and one of its important downstream effectors. It also strengthens the case for an unusually long dosing interval, because patients in two treatment arms received only one BEL512 injection during the 24-week efficacy period and nevertheless showed sustained activity, according to the company. What the announcement does not yet establish is equally important: Belenos has not disclosed the numerical treatment effects, confidence intervals, individual P values or detailed results for each dosing arm, meaning the clinical magnitude of the Phase 2 benefit cannot yet be independently evaluated from the topline disclosure.
BEL512 is known as CM512 in Greater China, where development is being led by Keymed Biosciences. Belenos holds development and commercialisation rights outside Greater China and is building a broader inflammatory-disease programme around the molecule that also includes asthma, chronic obstructive pulmonary disease, atopic dermatitis and chronic spontaneous urticaria.
What did the BEL512 Phase 2 trial actually test in patients with chronic rhinosinusitis with nasal polyps?
The Phase 2 study, registered as NCT06930612 and also known as NEZHA-1, enrolled 120 adults in China with inadequately controlled chronic rhinosinusitis with nasal polyps. Participants had a baseline Nasal Polyp Score of at least five, with at least two polyps in each nostril, together with a Nasal Congestion Score of two or three, identifying a population with substantial persistent disease rather than relatively mild nasal polyposis.
Patients were randomised to receive 300 mg of BEL512 every 12 weeks, 300 mg every 24 weeks, 600 mg every 24 weeks or placebo. All patients also received daily mometasone furoate nasal spray, allowing the study to test BEL512 as an add-on intervention rather than against the withdrawal of standard intranasal corticosteroid therapy. The treatment period lasted 24 weeks and was followed by another 12 weeks of safety follow-up.
The primary endpoint measured change from baseline in Nasal Polyp Score at Week 24. Secondary assessments included nasal congestion, loss of smell, total symptom score, the Lund-Mackay sinus computed tomography score and the 22-item Sinonasal Outcome Test, giving the programme a combination of objective polyp and imaging measures together with symptom and patient-reported assessments. Belenos reported statistically significant improvements over placebo across the primary and all these secondary measures at Week 24.
That breadth is potentially important because shrinking polyps without producing a parallel improvement in congestion, smell and quality of life would provide a less persuasive clinical proposition. Conversely, improvements across objective and patient-reported endpoints can make a Phase 2 dataset more relevant to later regulatory development. The unanswered question is how large those differences actually were, since statistical significance alone cannot establish whether the magnitude will prove clinically compelling in a larger and more geographically diverse Phase 3 population.
How strong is the evidence that BEL512 could support dosing only once every six months?
Dosing frequency could become one of BEL512’s most commercially interesting characteristics if later studies reproduce the Phase 2 findings. The 300 mg every-24-weeks and 600 mg every-24-weeks groups effectively tested a single injection across the study’s 24-week treatment period, while the 300 mg every-12-weeks group received repeat administration. Belenos said improvements were detectable as early as Week 4 and that activity remained durable through treatment and follow-up.
The long-interval hypothesis is supported by earlier pharmacokinetic work. A peer-reviewed first-in-human Phase 1 study of CM512 published in Frontiers in Immunology in May 2026 reported a terminal half-life of roughly 59 to 74 days across single-dose cohorts, together with low treatment-emergent immunogenicity and evidence of pharmacodynamic suppression of free TSLP and IL-13. The study was conducted in healthy volunteers, so it did not establish efficacy in chronic rhinosinusitis, but it provided a mechanistic and pharmacokinetic foundation for exploring substantially wider dosing intervals.
The commercial significance could be considerable if the profile survives Phase 3. Dupilumab, an established biologic for inadequately controlled chronic rhinosinusitis with nasal polyps, is administered every two weeks for the indication, while tezepelumab, which the United States Food and Drug Administration approved for CRSwNP in October 2025, is administered every four weeks. A validated BEL512 regimen given approximately every six months would therefore represent a substantial reduction in injection frequency.
That comparison is about treatment burden, not efficacy. BEL512 has not been evaluated head-to-head against these therapies, and separate clinical trials can differ materially in patient selection, baseline disease severity, endpoint definitions, background therapy and statistical methodology. Less frequent dosing would therefore be a differentiating feature only if Phase 3 establishes adequate efficacy, durability and safety.
Why does targeting both TSLP and IL-13 make BEL512 different from existing biologic strategies?
BEL512 is designed to inhibit two distinct components of type 2 inflammation. TSLP is an epithelial cytokine involved early in the inflammatory cascade, while IL-13 is a downstream cytokine associated with mucus production, tissue inflammation, epithelial barrier dysfunction and remodelling. Belenos is attempting to combine those mechanisms within one long-acting bispecific antibody rather than relying on inhibition of a single target.
The concept gives BEL512 an interesting position within an increasingly sophisticated inflammatory-disease pipeline landscape. Tezepelumab directly targets TSLP, while dupilumab blocks signalling through interleukin-4 receptor alpha and consequently inhibits IL-4 and IL-13 signalling. Other developers are also investigating multispecific approaches involving TSLP, IL-13, IL-4 receptor signalling and related inflammatory pathways, showing that the industry is increasingly examining whether broader pathway control can improve outcomes in heterogeneous type 2 inflammatory diseases.
However, dual targeting should not itself be interpreted as evidence of superior efficacy. A biologically attractive mechanism may fail to produce a clinically meaningful advantage, and blocking two inflammatory pathways within one molecule introduces its own dose-selection and development questions. BEL512 therefore still needs to demonstrate that the additional biological breadth translates into a benefit worth distinguishing from established monoclonal antibodies.
Phase 3 dose selection will be particularly revealing. If the lower 300 mg dose administered every 24 weeks delivers efficacy close to that of the higher or more frequently dosed regimens, Belenos could have a particularly attractive convenience proposition. If the fuller dataset instead shows a meaningful efficacy gradient between arms, developers may face a more conventional trade-off between dose intensity, durability and response.
What do the topline safety results tell us, and what information is still missing?
Belenos reported that treatment-emergent adverse-event rates were similar between BEL512 and placebo and said there were no severe treatment-emergent adverse events, serious adverse events or discontinuations within the BEL512 treatment groups. The company also described anti-drug antibody findings as minimal. Those observations are reassuring for a Phase 2 programme, particularly for an antibody intended for chronic administration.
The disclosure nevertheless remains topline. Belenos has not yet provided treatment-emergent adverse-event percentages by arm, treatment-related adverse events, individual event categories, laboratory changes or longer-term exposure data. The absence of serious or severe events in a 120-patient study is useful information, but a programme intended for broad chronic use will require substantially greater exposure before its safety profile can be characterised with confidence.
Earlier Phase 1 data provide some additional context. In healthy volunteers, treatment-related adverse events were reported as mild or moderate, no serious adverse events or deaths occurred, and treatment-emergent anti-drug antibody rates were low. Those findings support continued development but cannot substitute for longer-duration safety information in patients receiving a therapeutically active regimen.
Detailed Phase 2 presentation will therefore matter almost as much for safety interpretation as for efficacy. Belenos has said the complete results are expected to be presented at a scientific meeting and submitted to a peer-reviewed journal. Until that happens, the current evidence should be viewed as positive company-reported topline data rather than a fully assessable clinical dataset.
Does China’s Breakthrough Therapy designation materially change BEL512’s regulatory position?
Following the Phase 2 study, CM512 was included in the Breakthrough Therapy programme of the Center for Drug Evaluation under China’s National Medical Products Administration for chronic rhinosinusitis with nasal polyps. The designation provides an important regulatory signal around the programme and can facilitate closer interaction with the Chinese regulator during development.
It is not marketing authorisation, and it does not independently establish efficacy or confirm that a future application will be approved. Its immediate significance is that Keymed now has a regulatory pathway supporting accelerated engagement as it prepares to move CM512 into Phase 3 development in China.
Belenos plans a separate Phase 3 programme outside China in the first half of 2027. That programme will be particularly important because the current Phase 2 evidence was generated entirely in China, while eventual development across the United States and other markets will require data capable of supporting regulatory assessment in broader populations.
Can BEL512 turn a positive Phase 2 signal into a differentiated Phase 3 programme?
BEL512 has crossed an important development threshold. Meeting the Nasal Polyp Score primary endpoint alongside congestion, smell, imaging and quality-of-life measures gives Belenos a multidimensional efficacy signal rather than a result driven by a single isolated endpoint. The apparent persistence of activity following one injection in the 24-week dosing arms also provides a credible clinical reason to test the molecule aggressively as a long-interval therapy.
The next stage will be more demanding. The CRSwNP treatment environment now includes biologics with established Phase 3 evidence, regulatory approvals and growing clinical experience, including therapies targeting IL-4 and IL-13 signalling, IgE, IL-5 and TSLP. Tezepelumab’s 2025 United States approval also means that upstream TSLP inhibition is no longer merely an experimental strategy in nasal polyps.
BEL512 consequently does not just need another statistically positive study. Belenos will need Phase 3 evidence that clarifies the magnitude of polyp reduction, symptom improvement, durability, safety and the optimal dose while demonstrating that a six-month schedule does not sacrifice clinically meaningful disease control.
For now, the Phase 2 result materially strengthens the development case for BEL512 but stops short of establishing how competitive the therapy could become. The most consequential numbers are still missing from the public dataset. When Belenos and Keymed disclose the actual effect sizes across the three active regimens, the industry will be able to judge whether BEL512’s unusual combination of dual-pathway biology and very infrequent dosing represents a genuine clinical differentiation strategy or simply an intriguing Phase 2 signal heading into its most important test.
