Overview

Nerandomilast, marketed as Jascayd, is an orally administered selective phosphodiesterase-4B (PDE4B) inhibitor developed for adults with idiopathic pulmonary fibrosis (IPF) and progressive pulmonary fibrosis (PPF). It received FDA approval in 2025 for these indications. Its relevance to combination thinking comes from how it was tested: in large phase 3 trials it was given on top of existing antifibrotic background therapy rather than as a replacement. That design reflects a practical reality in fibrotic lung disease—patients are often already receiving pirfenidone or nintedanib, and any new agent must show benefit in that context.

The PDE4B Mechanism

PDE4B is an enzyme that breaks down intracellular cyclic AMP. By preferentially inhibiting this isoform, nerandomilast raises cAMP levels in inflammatory and structural lung cells, which in turn dampens pro-inflammatory cytokine release and fibroblast activation. The antifibrotic and immunomodulatory effects arise from this pathway rather than from direct scarring reversal, positioning the molecule as a modulator of the fibrotic cascade.

Evidence for Use With Background Therapy

In the FIBRONEER-IPF phase 3 trial, patients were randomized to nerandomilast 18 mg twice daily, 9 mg twice daily, or placebo, stratified by whether they were already taking nintedanib or pirfenidone. The primary endpoint was the change in forced vital capacity at 52 weeks. Most enrolled patients were on background antifibrotic treatment, and both nerandomilast doses showed a smaller decline in lung function than placebo across these subgroups. A separate trial, FIBRONEER-ILD, evaluated the same agent in a broader progressive fibrotic lung disease population.

Practical Combination Considerations

Because nerandomilast is administered as an oral tablet and was studied together with established antifibrotics, it fits a combination or add-on model. The most frequently reported adverse event in the clinical program was diarrhea. As with any antifibrotic regimen, therapy should be guided by a clinician who can monitor tolerance and adjust background medications.

FAQ

Q: Is nerandomilast a replacement for pirfenidone or nintedanib? A: In the pivotal trials it was studied as an add-on to existing antifibrotic therapy, not as a substitute, and treatment decisions should be made by the managing physician.

Q: What is the proposed mechanism of nerandomilast? A: It is a selective PDE4B inhibitor that raises intracellular cAMP, reducing inflammatory signaling and fibroblast activation involved in fibrosis.

Q: Which patients were studied in the phase 3 program? A: Adults with IPF in FIBRONEER-IPF and a broader progressive fibrotic lung disease population in FIBRONEER-ILD, most of whom were already on antifibrotic background therapy.