Our Take
KLN-1010 looks safer than ESOT-01 on paper, but the sample is tiny, follow-up is short, and we don't know if it works in patients who've already failed BCMA drugs.
Why it matters
In vivo CAR-T therapies skip the manufacturing step that makes autologous CAR-T expensive and slow, but safety and efficacy remain open questions. If KLN-1010 clears later trials with durable benefit, Eli Lilly could unlock a faster, cheaper route into relapsed myeloma—but the bar is high in a space already crowded with approved BCMA-targeting options.
Do this week
Oncology strategists: map which of your relapsed myeloma patients have prior BCMA therapy exposure, since KLN-1010's positioning hinges on whether it works in that population—Kelonia has not disclosed this breakdown.
Eli Lilly's KLN-1010 delivered responses across the board, but with caveats
Kelonia Therapeutics presented Phase I data for KLN-1010 at ASCO 2026 (May 29–June 2). The therapy is an in vivo lentiviral CAR-T targeting BCMA, infused directly without apheresis or manufacturing. All 18 patients enrolled showed response: nine partial responses, four very good partial responses, one complete response, and four stringent complete responses. Of the six patients evaluable at four months or longer, two maintained very good partial responses and four achieved stringent complete responses. One patient progressed despite a partial response and MRD-negative status at one month.
The safety signal was notably gentler than comparators. Four patients experienced grade 1 or 2 cytokine release syndrome managed with tocilizumab and corticosteroids. Two experienced immune effector cell–associated neurotoxicity syndrome, one grade 3, which resolved in three days. These results suggest outpatient administration may be feasible in future trials. All 18 patients achieved minimal residual disease negativity at one month, though one reverted to MRD-positive status by four months.
Eli Lilly acquired Kelonia in April 2026 for $3.25 billion upfront plus $3.75 billion in conditional milestones.
The safety advantage is real, but efficacy remains uncertain against established competitors
AstraZeneca's ESOT-01, another BCMA-targeting lentiviral in vivo CAR-T, presented in the Lancet in March 2026 (five patients). Three experienced grade 3 cytokine release syndrome. One patient with preexisting extramedullary disease suffered severe neurological decline and died of cardiac arrest. The four evaluable patients were MRD-negative: three stringent complete responses, one very good partial response. Side-by-side, ESOT-01 appears more efficacious but KLN-1010 safer.
The practical problem: KLN-1010's positioning is murky. J&J's Carvykti and Tecvayli are already approved for relapsed myeloma at first relapse. If KLN-1010 lands in third-line or later, many patients will have already been exposed to BCMA-targeting therapy and bispecific antibodies. The trial did not disclose how many of the 18 patients had prior BCMA treatment. If durability collapses in BCMA-refractory disease, the market window narrows sharply.
Both in vivo therapies remain early stage. KLN-1010 has only six patients with meaningful follow-up. Longer observation is required to confirm whether the safety gains hold and whether responses persist.
What to watch in the next 12 months
Three uncertainties will determine whether KLN-1010 becomes a clinical reality. First: does Eli Lilly expand the trial cohort and publish prior BCMA therapy exposure data. Second: do durability curves at 12 and 18 months in the Phase I cohort match or exceed ESOT-01's observed responses. Third: does safety remain manageable as dose escalation continues and more patients are treated. Until those gaps close, KLN-1010 remains a well-tolerated but unproven alternative to the autologous and bispecific BCMA landscape already in clinic. The field is crowded; in vivo CAR-T will have to prove it is faster and durable, not just safer.