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Syndax Stock Falls 16% as Phase II Fibrosis Study Misses Primary Goal

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Key Takeaways

  • Syndax shares fell 15.7% after its phase II fibrosis study of axatilimab failed to meet the primary endpoint.
  • MAXPIRe study showed no benefit in slowing FVC decline, despite axatilimab's favorable safety profile.
  • SNDX halts IPF development but continues cGVHD studies in earlier settings, with results due in 2026 and 2028.

Syndax Pharmaceuticals (SNDX - Free Report) shares fell 15.7% on Tuesday after the company reported that its mid-stage study of axatilimab in idiopathic pulmonary fibrosis (IPF) failed to meet the primary endpoint. The disappointing outcome led Syndax to discontinue plans to develop axatilimab for IPF.

Axatilimab, marketed as Niktimvo, is already approved by the FDA to treat chronic graft-versus-host disease (cGVHD) in adult and pediatric patients weighing at least 40 kilograms whose disease has not responded to at least two prior lines of systemic therapy. The drug is a first-in-class monoclonal antibody that blocks CSF-1R. Syndax is evaluating whether axatilimab can be used earlier in the cGVHD treatment pathway, in combination with standard-of-care therapies.

The phase II MAXPIRe study evaluated axatilimab in 145 IPF patients over 26 weeks. Enrolled patients were assigned in a 2:1 ratio to receive axatilimab 0.3 mg/kg or placebo every two weeks, with randomization stratified according to the use of background antifibrotic therapy.

SNDX's Phase II Fibrosis Study Data in Detail

Per Syndax, the MAXPIRe study did not meet its primary endpoint, which assessed the annualized rate of decline in forced vital capacity (FVC). FVC measures the volume of air a person can forcibly exhale after taking the deepest possible breath and is used to track changes in lung function. In IPF, a progressive lung disease marked by scarring, monitoring FVC helps researchers assess how quickly respiratory capacity deteriorates. Although the study was designed to determine whether axatilimab could slow this decline compared with placebo, the top-line findings did not establish a benefit on the study’s primary measure. Syndax did not provide detailed numerical efficacy comparisons in its announcement.

Year to date, SNDX shares have plummeted 33.6% against the industry’s 1.8% growth.

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Axatilimab was well tolerated in the phase II MAXPIRe study, with a safety and tolerability profile comparable to placebo and no new safety signals. Treatment-emergent adverse event rates leading to treatment discontinuation were low in both groups. The most common adverse events in the axatilimab arm were generally consistent with those reported in earlier studies, and neither group had treatment-related fatal adverse events. While the safety findings were reassuring, tolerability alone could not offset the failure to achieve the primary efficacy endpoint. The result means Syndax will not continue developing axatilimab for IPF, even though no unexpected safety concern emerged in the study.

Although the findings are a setback for Syndax's efforts to expand axatilimab into IPF, the company continues to pursue opportunities to use the drug in cGVHD. The results therefore leave its ongoing cGVHD development programs unaffected.

Syndax continues to advance axatilimab in cGVHD, including studies testing the drug alongside standard-of-care treatment in newly diagnosed patients. Its ongoing phase II study evaluating axatilimab in combination with ruxolitinib is expected to report top-line results in the fourth quarter of 2026, while the ongoing phase III study evaluating axatilimab with corticosteroids is expected to report results in early 2028.

SNDX’s Zacks Rank & Stocks to Consider

Syndax currently carries a Zacks Rank #4 (Sell).

Some better-ranked stocks in the biotech sector are Amarin (AMRN - Free Report) and Corcept Therapeutics (CORT - Free Report) , each currently sporting a Zacks Rank #1 (Strong Buy) and Aldeyra Therapeutics (ALDX - Free Report) , carrying a Zacks Rank #2 (Buy). You can see the complete list of today’s Zacks #1 Rank stocks here.

Over the past 60 days, loss per share estimates for Amarin have narrowed from 65 cents to 39 cents for 2026. Over the same period, estimates for 2027 loss per share have narrowed from 51 cents to 50 cents. AMRN’s shares have lost 17% year to date.

Amarin’s earnings beat estimates in three of the trailing four quarters and missed in the remaining one, the average surprise being 62.27%.

Over the past 60 days, earnings per share estimates for Corcept Therapeutics have increased from $1.13 to $1.86 for 2026. Over the same period, estimates for 2027 earnings per share have risen from $2.35 to $3.48. CORT’s shares have surged 238.5% year to date.

Corcept Therapeutics’ earnings missed estimates in two of the trailing four quarters, beat in one, while meeting in the remaining occasion, with the average surprise being 240.74%.

Over the past 60 days, loss per share estimates for Aldeyra Therapeutics have narrowed from 43 cents to 39 cents for 2026. Over the same period, estimates for 2027 loss per share have narrowed from 22 cents to 16 cents. ALDX’s shares have plunged 82.6% year to date.

Aldeyra Therapeutics’ earnings beat estimates in each of the trailing four quarters, delivering an average surprise of 29.25%.

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