Lacutamab

Lacutamab is a first-in-class antibody from Innate Pharma that targets KIR3DL2, a surface protein that the malignant T cells in Sézary syndrome and some mycosis fungoides patients carry but normal tissues largely don't. The TELLOMAK Phase 2 program (NCT03902184) is testing it in advanced cutaneous T-cell lymphoma as a single agent and in peripheral T-cell lymphoma in combination with chemotherapy [1]. The Sézary syndrome cohort is the lead path to market: this is a rare, aggressive blood-borne CTCL with few good options after mogamulizumab (anti-CCR4 antibody, approved 2018), and KIR3DL2 is expressed on the cancer cells in the large majority of these patients, giving the antibody a clean target [2]. Long-term TELLOMAK follow-up presented at ASCO 2025 showed an ORR of 42.9% (95% CI 31.4-55.1) and a median duration of response of 25.6 months in heavily pretreated Sézary patients post-mogamulizumab, which is the headline signal [8]. The commercial question is whether Innate Pharma - a mid-cap French biotech now navigating a tight cash runway - can finance and execute the planned TELLOMAK-3 confirmatory Phase 3 alone or whether this asset gets partnered. The scientific question is whether the Phase 2 signal holds under randomized confirmation.

Novel biologic, never approved anywhere. The key-intent Phase 2 in Sézary and mycosis fungoides (TELLOMAK, NCT03902184) has completed enrollment with 170 patients [3]. A separate Phase 2 in relapsed/refractory peripheral T-cell lymphoma is enrolling through the Lymphoma Academic Research Organisation (NCT04984837, n=56) and is biomarker-selected for KIR3DL2 expression [4]. A Phase 1 KIR3DL2-selected PTCL study (NCT05321147) has completed [5]. Lacutamab carries FDA orphan drug designation for CTCL and FDA fast track for relapsed/refractory Sézary syndrome, plus EMA PRIME for Sézary - designations that unlock rolling review and earlier FDA dialogue, which a small sponsor needs. Innate has publicly committed to a randomized confirmatory Phase 3 (TELLOMAK-3) targeting H2 2026 initiation, with a Sézary cohort intended to support accelerated approval and a mycosis fungoides cohort for full approval [9]. Initiation is explicitly contingent on securing non-dilutive financing (partnership or royalty), reflecting a constrained cash position [9]. There is no BLA on file yet; a US filing in 2027 is plausible only if FDA accepts the TELLOMAK Phase 2 Sézary cohort as the basis for accelerated approval with TELLOMAK-3 as the confirmatory trial.

KIR3DL2, also called CD158k, is normally an inhibitory receptor on a subset of natural killer cells and CD8+ T cells - when it binds HLA-A3 and HLA-A11, it tells the NK cell to stand down [6]. In Sézary syndrome and a meaningful fraction of mycosis fungoides and peripheral T-cell lymphomas, the malignant T cells switch this receptor on aberrantly and display it at high density on their surface; in advanced Sézary, KIR3DL2 is detectable on the malignant clone in roughly 80-90% of patients, and expression density on tumor cells substantially exceeds that on normal NK cells [2]. Lacutamab is a humanized antibody with an Fc region engineered to enhance ADCC - antibody-dependent cellular cytotoxicity, where the antibody coats the cancer cell and recruits NK cells and macrophages to kill it. The therapeutic window argument rests on differential expression: tumor cells are KIR3DL2-high while normal NK cells are KIR3DL2-low and only a minority of NK cells express it at all, so the dominant effect is tumor killing rather than NK depletion. Consistent with this, the Phase 1 first-in-human study (IPH4102-101, Bagot et al. Lancet Oncol 2019) reported manageable safety with no signal of clinically meaningful NK depletion or opportunistic infection, and demonstrated an ORR of ~36% in heavily pretreated Sézary patients with responses concentrated in KIR3DL2-positive disease [7]. The case is genetics-light (no driver mutation) but expression-heavy and target-clean, which is the standard pattern for antibody drugs in heme malignancy.

TELLOMAK (NCT03902184) is a multi-cohort, open-label Phase 2 with overall response rate as the primary endpoint [3]. Cohorts split by histology: Sézary syndrome (relapsed/refractory after at least two prior systemic therapies including mogamulizumab - an anti-CCR4 antibody approved in 2018 and the current standard second-line option that lacutamab trials require patients to have already failed), mycosis fungoides stratified by KIR3DL2 expression, and a peripheral T-cell lymphoma arm combining lacutamab with GEMOX (gemcitabine plus oxaliplatin, a standard chemotherapy doublet used in relapsed PTCL). Total enrollment of 170 is split unevenly across cohorts. Single-arm design is the obvious limitation, but in rare CTCL it is also the regulatory norm - both mogamulizumab and brentuximab vedotin earned CTCL approvals on similarly designed studies. The PTCL Phase 2 (NCT04984837) is biomarker-selected for KIR3DL2 expression and uses modified PFS as the primary endpoint (progression-free survival measured from first dose, with modified rules for assessing skin and visceral disease in T-cell lymphomas), which is a higher bar than ORR and the right one for a chemotherapy combination [4]. The unanswered design question - now partially resolved - is that the FDA appears to require randomized confirmation: Innate has committed to TELLOMAK-3, an open-label randomized Phase 3 in Sézary and mycosis fungoides, planned for H2 2026 initiation [9]. The comparator and exact regulatory choreography (whether accelerated approval comes before or alongside Phase 3 readout) remain the key open variables.

Our model gives this drug a 17% chance of eventually reaching approval. That starts from a historical baseline of about 21% for Phase 2 drugs in this area, then shifts based on ten facts about the trial and its sponsor. The estimate gets a small boost from the trial's non-randomized design and open-label blinding, but is pulled down by the sponsor's thin approval record and weak earlier-phase results. The remaining factors fall close to average, so they leave the final number near where the baseline started.

Efficacy: the TELLOMAK Sézary signal needs to hold under independent central review in TELLOMAK-3. Single-arm Phase 2s in CTCL have a history of looking better than randomized follow-up - investigator-assessed responses in skin-predominant disease are notoriously soft. The mycosis fungoides cohort has been the weaker performer, and if the FDA labels narrowly to Sézary only, the addressable patient pool is small: US Sézary incidence is approximately 300-500 new cases per year (~0.1 per 100,000), with an estimated prevalent, treatment-eligible pool of roughly 2,000-4,000 patients cycling through lines of therapy [10]. The prevalent pool is the commercially relevant denominator. Safety: infusion reactions and cytokine release are the predictable on-mechanism risks, manageable but real. The theoretical concern of NK cell depletion has not surfaced as a clinical problem in Phase 1 or 2. No black-box-class signals have emerged. Execution and financing: Innate Pharma reported €25.4M cash as of March 31, 2026, with guided runway only to end of Q3 2026 [9]. TELLOMAK-3 initiation is explicitly contingent on securing non-dilutive financing (partnership or royalty deal); without such a deal, the company faces either a dilutive raise or further pipeline cuts before BLA. The AstraZeneca partnership covers monalizumab, not lacutamab, so this asset is unpartnered for commercial. Regulatory: the open questions are whether ORR with durable DoR is sufficient as the registrational endpoint and whether accelerated approval can be obtained on TELLOMAK data with TELLOMAK-3 as confirmatory. Commercial: the CTCL space already has mogamulizumab (Kyowa Kirin) and brentuximab vedotin (CD30+ disease), so lacutamab must differentiate on the post-mogamulizumab patient - the long-term DoR of 25.6 months supports this positioning. IP: lacutamab composition-of-matter patents extend into the early 2030s; precise expiry varies by jurisdiction and exclusivity extensions, but the IP window is acceptable for an acquirer.

Worth watching, with two near-term triggers. (1) A partnership or royalty financing announcement before Q3 2026 - without one, the TELLOMAK-3 timeline slips and dilution risk rises sharply. (2) Any FDA alignment confirming the accelerated approval pathway based on TELLOMAK Sézary data. Either trigger alone is interesting; both together is the buy signal. For Innate Pharma specifically (Euronext: IPH, Nasdaq: IPHA), the stock has historically traded on monalizumab readouts more than lacutamab, which means lacutamab good news is asymmetric - a Sézary approval would be the company's first commercial product and likely trigger broader partnership or acquisition discussions. The acquirer logic is clear: a heme-onc commercial player with CTCL reach (Kyowa Kirin already sells mogamulizumab and would have the cleanest channel, but BMS, Pfizer, or Lilly could rationalize the addition). The financing constraint also makes Innate a more motivated counterparty than it was 12 months ago. Check the next Innate earnings call for partnership progress, and ASH 2026 for additional TELLOMAK long-term data and any first signal from the biomarker-selected PTCL Phase 2.