Nerandomilast: PDE4B Inhibitor Rewrites IPF Standard of Care
Nerandomilast (Jascayd) won FDA approval in 2025 for adult IPF and PPF. We decode preferential PDE4B inhibition and FIBRONEER-IPF trial data.
Ofev/Esbriet Don't Stop It—That's the Reality
IPF's standard-of-care drugs—Pirfenidone and Nintedanib—only "slow progression." Patients still lose lung function. And many discontinue due to side effects.
Enter Nerandomilast (Jascayd), a preferential PDE4B inhibitor. By designing for preferential PDE4B over PDE4D inhibition (aiming to mitigate PDE4D-associated central side effects), it showed FVC-decline reduction in FIBRONEER-IPF—a Phase 3 trial that stratified patients by baseline antifibrotic therapy1.
BI 1015550 (Nerandomilast): Precise Molecular Design
BI 1015550 (Nerandomilast), developed by Boehringer Ingelheim and approved in the US (October 7, 2025) as Jascayd6, is an oral drug that preferentially inhibits phosphodiesterase 4B (PDE4B).
Why PDE4"B"? The Key to Overcoming Side Effect Barriers
PDE4 inhibitors themselves are not a new concept (e.g., the COPD drug roflumilast). They exert anti-inflammatory effects by increasing cAMP levels, but traditional "non-selective" PDE4 inhibitors had a dilemma where severe central side effects such as nausea and vomiting became dose-limiting factors, preventing the administration of sufficiently effective doses.
BI 1015550 broke through this barrier with "selectivity."
- PDE4B: A subtype expressed in inflammatory cells and fibroblasts, involved in pathogenesis.
- PDE4D: A subtype expressed in the vomiting center of the brain, involved in side effects such as nausea.
BI 1015550 is designed as a "preferential PDE4B inhibitor" — the exact phrasing used in the Phase 2 NEJM 2022 paper title2 — with higher inhibitory activity against PDE4B than PDE4D. The design intent is to mitigate PDE4D-associated central side effects (e.g., nausea, vomiting) while still engaging the PDE4B pathway to deliver anti-inflammatory and anti-fibrotic effects. Because it is administered orally, systemic exposure exists; the drug is not selectively restricted to lung lesions.
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Clinical Trial Data: Statistical Significance and Its Meaning
Phase 2 Trial Results (NEJM 2022)
The n=147 Phase 2 trial (NCT04419506) showed FVC-decline differences vs placebo2.
- FVC Change (at 12 weeks):
- BI 1015550 monotherapy: median +5.7 mL (95% credible interval -39.1 to +50.5) vs placebo -81.7 mL — suggesting stabilization of disease activity.
- Background-therapy subgroup (exploratory):
- Among patients on existing standard of care drugs (pirfenidone or nintedanib) at baseline, an FVC-decline reduction trend was observed when BI 1015550 was added on. This is an exploratory subgroup analysis positioned as the rationale for confirming add-on efficacy in Phase 3, not as definitive proof of combination effect.
Phase 3 Trial (FIBRONEER-IPF, NEJM 2025)
In the Phase 3 FIBRONEER-IPF trial (NCT05321069), reported in N Engl J Med 2025;392(22):2193-2202, 1,177 IPF patients (77.7% on pirfenidone or nintedanib at baseline) were randomized to Nerandomilast 9 mg / 18 mg or placebo. Patients were stratified by background antifibrotic therapy1.
- Primary Endpoint (FVC change at 52 weeks, ITT):
- Nerandomilast 18 mg: -114.7 mL (95% CI -141.8 to -87.5); p<0.001 vs placebo
- Nerandomilast 9 mg: -138.6 mL (95% CI -165.6 to -111.6); p=0.02 vs placebo
- Placebo: -183.5 mL (95% CI -210.9 to -156.1)
- The pattern of FVC-decline reduction was broadly consistent across the strata defined by background antifibrotic use.
- Safety: The most frequent adverse event was diarrhea, mostly mild to moderate, supporting tolerability over the 52-week trial. Approval-level safety and dosing details should be read from the Jascayd prescribing information6.
- Secondary Endpoints: The composite of "acute exacerbation, respiratory hospitalization, or death" did not show a clear between-group difference, leaving long-term follow-up and real-world data as open questions.
In parallel, the LPA1 receptor antagonist admilparant (BMS-986278) reported Phase 2 efficacy and safety data in IPF and PPF (Am J Respir Crit Care Med 2025;211(2):230-238, NCT04308681)4. Whether an LPA1-pathway agent like admilparant could complement preferential PDE4B inhibition with nerandomilast in future combination strategies remains a hypothesis to evaluate; head-to-head or combination clinical data are not yet available.
Others: Challenge of Local Delivery by Inhaled Drugs
Another approach to avoid systemic side effects is "inhaled drugs."
- Inhaled Pirfenidone (AP01, Avalyn Pharma, etc.):
- AP01 was evaluated in a randomized, open-label, dose-response trial in IPF (Thorax 2023;78(9):882-889, West A et al.)5, assessing the safety and tolerability of a strategy that aims to keep blood concentrations low while increasing lung-tissue concentrations. Development continues as an option distinct from oral therapy.
Conclusion
IPF drug discovery entered a new phase with the US FDA approval of the preferential PDE4B inhibitor Nerandomilast (brand name Jascayd) on October 7, 20256. The conversation is shifting from "slowing progression" toward "maintaining function and improving QOL."
For regions outside the US (including Japan), the approval status as of this article's publication (May 2026) is that regulatory review or filing processes appear to be ongoing at each agency; a specific timeline cannot be inferred from public information alone. Please refer to PMDA / Boehringer Ingelheim official announcements for the latest status.
According to the Jascayd label, the approved indications are "treatment of idiopathic pulmonary fibrosis in adult patients" and "treatment of progressive pulmonary fibrosis in adult patients" as standalone monotherapy indications6; both FIBRONEER-IPF and FIBRONEER-ILD allowed concurrent use of background antifibrotic therapy (stratified in the trial design). How nerandomilast will be used in real-world practice (monotherapy vs add-on share, eligible patient populations) will become clearer as guidelines are updated and prescribing data accumulate.
References & Clinical Trials
1. Richeldi L, Azuma A, Cottin V, et al. Nerandomilast in Patients with Idiopathic Pulmonary Fibrosis. N Engl J Med. 2025;392(22):2193-2202. PubMed / NCT05321069
2. Richeldi L, Azuma A, Cottin V, et al. Trial of a Preferential Phosphodiesterase 4B Inhibitor for Idiopathic Pulmonary Fibrosis. N Engl J Med. 2022;386(23):2178-2187. PubMed / NCT04419506
3. Richeldi L, Azuma A, Cottin V, et al. Design of a phase III, double-blind, randomised, placebo-controlled trial of BI 1015550 in patients with idiopathic pulmonary fibrosis (FIBRONEER-IPF). BMJ Open Respir Res. 2023;10(1):e001563. PubMed
4. Corte TJ, Behr J, Cottin V, et al. Efficacy and Safety of Admilparant, an LPA1 Antagonist, in Pulmonary Fibrosis: A Phase 2 Randomized Clinical Trial. Am J Respir Crit Care Med. 2025;211(2):230-238. PubMed / NCT04308681
5. West A, Chaudhuri N, Barczyk A, et al. Inhaled pirfenidone solution (AP01) for IPF: a randomised, open-label, dose-response trial. Thorax. 2023;78(9):882-889. PubMed
6. FDA. Jascayd (nerandomilast) Prescribing Information. Boehringer Ingelheim Pharmaceuticals; revised December 2025. DailyMed current label