KURA, SNDX: 40% of Menin Inhibitor Use Is Off-Label Combination

Kura Oncology (KURA) and Syndax Pharmaceuticals (SNDX) each told investors in early August 2026 that roughly 40% of menin inhibitor use is physician-initiated combination therapy, even though both products are approved only as single agents [1][2]. Two companies with different products, different sales forces and different data sources landed on the same share.

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The label covers monotherapy; prescribers add the drug to regimens already in use

Both products treat relapsed or refractory acute myeloid leukemia (AML), a cancer in which immature blood cells multiply in the bone marrow. First-line treatment is chemotherapy, and options after relapse have been scarce. Menin inhibitors are a recently approved class of oral targeted drugs that work only in patients carrying an NPM1 mutation or a KMT2A rearrangement, and both approved products are labeled for use on their own [1][2].

What prescribers changed is where the drug sits in the regimen. They add it on top of venetoclax (an oral drug that restores cell death in leukemia cells) plus azacitidine (a hypomethylating chemotherapy), or on top of a FLT3 inhibitor in patients who also carry a FLT3 mutation [2].

Two obstacles that used to block that behavior are gone. Physicians worried that stacking a new agent on an existing regimen would worsen myelosuppression — a deeper drop in blood counts — and the combination data landed this quarter. On reimbursement, Kura said more than 95% of covered lives have access with no label restrictions, so payers do not stand between the physician and either choice [2].

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Two independent data sources report the same share, and duration is lengthening

The two companies drew on entirely different evidence and arrived at the same number. Syndax used purchased claims data showing 75% of use in the second and third line and about 40% in combination [1]. Kura used its own new-patient-start data: $9.1 million in second-quarter net product revenue, roughly 115 new patient starts, about 40% of them physician-initiated combinations, consistent with the prior quarter at lower volume — while the company promotes only the approved monotherapy indication [2][3].

Treatment duration is the variable to watch. Syndax disclosed that patients who do not go to transplant now average more than seven months on therapy; patients who pause three to six months for a stem cell transplant and then resume average at least nine months. About 50% of transplant patients have resumed therapy, up from an estimated 45% in the prior quarter, and management expects 70% to 80% eventually to return for one to two years [1].

The clinical data that supports this prescribing also arrived this quarter. Kura said results from the relapsed/refractory study of ziftomenib with venetoclax and azacitidine were published in Blood, with an 87% overall response rate in venetoclax-naive patients and median overall survival not reached at almost 11 months of follow-up. In a separate frontline dataset of 99 newly diagnosed patients treated with intensive chemotherapy, 12-month overall survival was 94% and median overall survival was not reached after 17.6 months of median follow-up, with no meaningful added myelosuppression [2].

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Revenue in this class turns on prescribing habit rather than on the label

Revenue here is new patient starts multiplied by how long each patient stays on therapy, and the second term is being set by clinical practice. Manufacturers can only promote the single-agent label, while what actually determines duration is how physicians build the regimen and whether patients resume after transplant. The control point therefore sits with the prescriber and with post-transplant follow-up, not with the commercial organization. Reimbursement adds no gate, since combination use requires no separate authorization.

The boundary matters. Duration is an expectation rather than an observed result: asked about it, Kura's commercial head said it will come over time and that the company is currently managing to getting every new patient started [2]. NCCN guideline inclusion is unresolved, and off-label combination use does not carry the protection a compendia listing would, so a payer policy change could reverse the behavior [3]. Syndax also offered a simpler explanation for its own growth — of roughly 4,500 relapsed/refractory NPM1 patients a year, fewer than 15% have received a menin inhibitor, so filling the labeled indication is enough to account for current volume [1].

Two things can be checked later: whether the disclosed average treatment duration and combination share keep rising, and whether guidelines take up combination regimens once the frontline Phase 3 programs read out [1][2].

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Companies exposed to this change

• AbbVie (ABBV): It owns venetoclax, the most common partner in the combinations physicians are building themselves. The more menin inhibitor use there is and the longer each patient stays on therapy, the more venetoclax courses are written alongside it — though neither company has disclosed how much volume that represents [2].
• Astellas Pharma (4503.T): It owns the FLT3 inhibitor gilteritinib. Kura said roughly half of NPM1-mutated patients also carry a FLT3 mutation, and those patients are exactly the group in which the two targeted drugs are being combined [2][4].

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Sources

[1] Drillr · Syndax Pharmaceuticals (SNDX) · 2026-08-04 · Q2 FY2026 earnings call

"Claims data show 75% of use in the second and third line and approximately 40% of use in combination."

[2] Drillr · Kura Oncology (KURA) · 2026-08-12 · Q2 FY2026 earnings call

[3] Drillr · Kura Oncology (KURA) · 2026-05-12 · Q1 FY2026 earnings call

[4] Drillr · Astellas Pharma (4503.T) · 2026-08-13 · ticker_lookup symbol check

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