ENV-101 (Taladegib, Hedgehog) IPF Phase 2a: Lung Volume Gain
Endeavor's ENV-101 (taladegib): oral SMO antagonist. Ph2a primary EP ppFVC +3.95% (p=0.035), exploratory TLC +257 mL (Lancet 2025). WHISTLE-PF enrolled.
Introduction: An Oncology Molecule Repurposed for IPF
One of the most talked-about candidates in the IPF pipeline is ENV-101 (taladegib / formerly LY2940680), an oral Smoothened (SMO) antagonist developed by Endeavor BioMedicines (San Diego). Taladegib was originally created by Eli Lilly for basal cell carcinoma (BCC); Endeavor repurposed it for pulmonary fibrosis after acquiring the asset via Ignyta.
In the Phase 2a trial ENV-IPF-101 (NCT04968574), 12 weeks of oral dosing produced a between-group difference in TLC of +257.0 mL (p=0.0040), a rare "absolute lung-volume gain" signal in IPF[1]. In 2025 the EMA granted PRIME designation (the first for IPF), and FDA / EC granted Orphan Drug Designation[2][3]. The Phase 2b WHISTLE-PF trial (NCT06422884) is now ongoing[4].
This article reviews ENV-101's mechanism, clinical data, competitive context, and preclinical considerations using only public sources.
1. Compound Profile
| Item | Detail |
|---|---|
| Generic name | Taladegib |
| Development codes | ENV-101 (Endeavor), LY2940680 (legacy Lilly) |
| Sponsor | Endeavor BioMedicines, Inc. (San Diego) |
| Modality | Oral small-molecule, selective Smoothened (SMO) antagonist (IC50 ≈ 4.56–7.64 nM) |
| Dose | 200 mg PO QD (Phase 2a) |
| Indication | Idiopathic pulmonary fibrosis (IPF) |
| Status | Phase 2a complete (ENV-IPF-101); Phase 2b ongoing (WHISTLE-PF) |
| Regulatory designations | EMA PRIME (first in IPF), FDA / EC Orphan Drug Designation |
| Origin | Created by Lilly for oncology → repurposed by Endeavor via Ignyta for IPF |
Taladegib retains activity against the SMO D473H vismodegib-resistance mutation, a notable SMO-pharmacology feature.
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2. Disease Context: Why "Reversal" Is the Missing Outcome
Current SOC (pirfenidone, nintedanib) halves the rate of FVC decline but does not improve lung function. The underlying pathology — aberrant repair initiated by damaged AEC2 cells and accumulation of scar tissue — has long been considered essentially irreversible.
The Hedgehog pathway is one reason this irreversibility persists. A developmental program that should be silent in adult lung is reactivated ("resurrected") in IPF, driving fibroblast-to-myofibroblast transition and ECM deposition[5]. ENV-101 aims to shut down this reactivated developmental pathway, enabling intervention not only to slow progression but potentially to restore lung structure.
3. Mechanism of Action: Hedgehog Blockade via SMO Antagonism
Pathway Overview
Sonic Hedgehog (SHH) binding to the PTCH1 receptor relieves PTCH1's inhibition of SMO, which activates GLI1/2 transcription factors. This cascade is essential for fetal lung development but is typically silent in mature lung.
Hedgehog Reactivation in IPF
In IPF lung, Hedgehog signaling is reactivated in both mesenchymal and epithelial compartments, increasing fibroblast proliferation, migration, and collagen / fibronectin production 2- to 3-fold (Bolaños et al., Am J Physiol Lung Cell Mol Physiol 2012)[6]. Human lung fibroblasts require primary cilia–dependent GLI transcription for TGF-β1-driven myofibroblast differentiation (Cigna et al., Am J Pathol 2012)[7].
Taladegib's Action
Taladegib competitively binds SMO, blocks GLI activation, and suppresses myofibroblast differentiation and ECM synthesis. Because it operates on a pathway orthogonal to SOC, there is a theoretical case for combination therapy.
4. Clinical Evidence: ENV-IPF-101 Phase 2a (12 Weeks)
| Item | Detail |
|---|---|
| Design | Multicenter (16 sites: Australia, Canada, Malaysia, Mexico, Korea), randomized, double-blind, placebo-controlled |
| N | 41 (taladegib 21 / placebo 20) |
| Dose & Duration | 200 mg PO QD for 12 weeks + 6-week follow-up |
| Primary outcomes | Safety (ITT population); change from baseline in FVC (efficacy-evaluable population) |
| Exploratory outcomes | HRCT-derived measures (TLC, quantitative ILD (QILD), etc.) |
Key Results[1]
- ppFVC change from baseline at Week 12 (primary outcome): taladegib +1.9%, placebo −1.3%, between-group difference +3.95% (95% CI 0.31–7.60, p=0.035) — statistically significant
- TLC change (HRCT-derived, exploratory): taladegib +206.67 mL, placebo −55.58 mL, between-group difference 257.0 mL (95% CI 86.8–427.2, p=0.0040)
- Quantitative ILD (QILD, HRCT-derived, exploratory): taladegib −9.4%, placebo +1.1%, p=0.047 (signal of reduced fibrotic burden)
- Pulmonary vessel volume significantly reduced (exploratory)
Note: absolute FVC (mL) is not separately reported in the Lancet Respir Med 2025 abstract (results reported as percent predicted).
Safety (Hedgehog-class characteristic AEs, all Grade 1–2):
- Dysgeusia: 57%
- Muscle spasms: 57%
- Alopecia: 52%
These AEs are well-characterized across the SMO inhibitor class. At Phase 2a Week 12, all events were Grade 1–2, with no serious related AEs and no deaths, confirming short-term tolerability; long-term tolerability over chronic dosing remains to be established (see "8. Points to Watch" #3 below). Results were presented at ERS 2025 (ALERT session) and published in Lancet Respiratory Medicine 2025[1].
5. WHISTLE-PF Phase 2b (NCT06422884)
| Item | Detail |
|---|---|
| Design | Global multicenter, randomized, double-blind, placebo-controlled, dose-ranging |
| Indication | IPF |
| Duration | 6 months |
| Status | Enrollment complete (n=213 ACTUAL, ACTIVE_NOT_RECRUITING), ClinicalTrials.gov verified 2026-02 |
WHISTLE-PF is positioned to test reproducibility and dose-response of the TLC signal from Phase 2a[4]. The ClinicalTrials.gov "Conditions" field lists both Idiopathic Pulmonary Fibrosis and Progressive Fibrosing Interstitial Lung Disease (PFILD), but all four current arms (Low / Mid / High dose + Placebo) are explicitly labeled "IPF Population" — a dedicated PPF arm or expansion plan is not yet visible in public sources.
6. Competitive Landscape
- SOC: pirfenidone, nintedanib — slow FVC decline but do not improve function.
- Nerandomilast (BI 1015550): PDE4B selective inhibitor; approved 2025.
- Rentosertib (ISM001-055): TNIK inhibitor; Phase 2a FVC +98.4 mL vs −20.3 mL at 12 weeks.
- Buloxibutid (C21): AT2R agonist; Phase 2a FVC +216 mL at 36 weeks (single-arm).
- Admilparant (BMS-986278): LPA1 antagonist; ALOFT Phase 3 ongoing.
- Oncology-approved SMO inhibitors: vismodegib (2012), sonidegib (2015), glasdegib (2018) — none with a formal fibrosis clinical program in the public record.
No other Hedgehog/SMO inhibitor has a confirmed clinical development path in pulmonary fibrosis, so ENV-101 retains a first-in-class position within the SMO class for fibrosis.
7. Preclinical Evaluation
ENV-101-specific preclinical data (bleomycin mouse efficacy values, etc.) are not detailed in Endeavor's public materials; peer-reviewed publications are expected. Meanwhile, the antifibrotic case for Hedgehog blockade is supported by Bolaños 2012[6] and Cigna 2012[7]. Suitable evaluation package to probe Hedgehog MOA:
- Bleomycin intratracheal mouse model: fibrotic area, hydroxyproline, Ashcroft score — see Bleomycin Lung Fibrosis Model Pitfalls.
- TGF-β1-induced myofibroblast differentiation in human lung fibroblasts: αSMA, collagen I, GLI1/2 reporter.
- Primary cilia immunostaining (acetylated α-tubulin): direct readout of Hedgehog responsiveness.
For broader model and endpoint design, see PCLS Ex Vivo Fibrosis Assessment and Multiplex Immunofluorescence for Fibrosis.
8. Points to Watch
- WHISTLE-PF readout: whether the TLC improvement reproduces over 6 months in a larger, placebo-controlled cohort.
- FVC between-group effect: whether Phase 2a's TLC advantage also emerges as a clear FVC delta.
- Long-term tolerability of SMO-class AEs (dysgeusia, alopecia, muscle spasms): BCC-era experience suggests dose strategy implications for chronic fibrosis dosing.
- Combination development: pairings with existing SOC or other next-gen candidates.
- PPF expansion: whether progressive pulmonary fibrosis (PPF) is formally added as an indication.
- Phase 3 design: leveraging EMA PRIME designation for accelerated late-stage development.
References
1. Maher TM, et al. Taladegib for the treatment of idiopathic pulmonary fibrosis (ENV-IPF-101): a multicentre, randomised, double-blind, placebo-controlled, phase 2a trial. Lancet Respir Med. 2025. PubMed 41043447 / Lancet Respir Med / ClinicalTrials.gov: NCT04968574 / Endeavor press release
2. Endeavor BioMedicines. EMA PRIME Designation for taladegib (ENV-101) in IPF. Endeavor press release
3. BusinessWire. Endeavor BioMedicines Receives Orphan Drug Designation from FDA and EC for Taladegib (ENV-101). July 2025. BusinessWire
4. Endeavor BioMedicines. First Patient Dosed in Phase 2b WHISTLE-PF. Endeavor press release / ClinicalTrials.gov: NCT06422884
5. Hedgehog in IPF "Resurrection Time" review. IJMS. 2022. PubMed 35008597
6. Bolaños AL, et al. Role of Sonic Hedgehog in Idiopathic Pulmonary Fibrosis. Am J Physiol Lung Cell Mol Physiol. 2012. PubMed 23023967
7. Cigna N, et al. The Hedgehog system machinery controls transforming growth factor-β-dependent myofibroblastic differentiation in humans. Am J Pathol. 2012. PubMed 23031257
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