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AACR IO 2026 — Notable readouts

Clinical and translational data presented at AACR IO 2026. Thirty-five late-breaking and clinical-trial abstracts were published (DOIs dated 2026-03-18); these are the ones with the most substance behind them.

All abstracts follow the DOI pattern 10.1158/2326-6074.io2026-<id>.

OBX-115 — engineered TIL in advanced melanoma

The best-documented readout of the meeting, and the only one with a full public poster PDF.

  • Abstract LB-A010 — "Translational data validate OBX-115 mechanism of action: Impact of dosing on clinical outcome in advanced (adv) melanoma" · DOI 10.1158/2326-6074.io2026-lb-a010
  • Trial: Agni-01, single-arm Phase 1/2, NCT06060613
  • Sponsor: Obsidian Therapeutics
  • Presenting author: Gino K. In (USC Norris); senior author Jason A. Chesney (UofL Brown Cancer Center); co-authors include Shoushtari (MSKCC), Amaria (MD Anderson), Betof (Stanford), Moyers (The Angeles Clinic)

Mechanism — the reason this one matters. OBX-115 is a tumor-infiltrating lymphocyte product expressing membrane-bound IL-15 regulated by acetazolamide, an already-approved small molecule. The regulated mbIL15 abrogates the need for systemic IL-2, which is the toxicity that has kept TIL therapy confined to centers able to manage it. Removing IL-2 widens eligibility more than any efficacy increment would.

Data reported:
Total treated 11 (DL1 n=3, DL2 n=2, DL3/RP2D n=6)
ORR at DL3 / RP2D 67% (4/6)
Complete responses at DL3 / RP2D 2 (33%)
ctDNA eVAF declined by Day 14 in all evaluable patients
PD-1 expression <1% on peripheral CD8+ and CD3+CD56+ cells through Day 56

Read the denominators before the response rate. Six patients at the recommended Phase 2 dose is hypothesis-generating, not practice-changing. The mechanism and the ctDNA kinetics are the durable contributions here.

Poster PDF (company-hosted, open): https://obsidiantx.com/wp-content/uploads/2026/02/AACR-IO-2026_Agni-01-Translational_2026-02-10_FINAL.pdf

OncLive covered this as "OBX-115 With Acetazolamide Induces Safe and Durable Antitumor Responses in Advanced Melanoma," but the article is Cloudflare-protected and its body text is unverified here.

Related: Parameswaran Hari of Obsidian Therapeutics spoke in MS6 (TILs and Maintenance of Immunity).

Obrixtamig (BI 764532) — DLL3×CD3 T-cell engager

Five abstracts — the largest single-program block at the meeting. Boehringer Ingelheim brought a coordinated data package rather than a single readout.

Abstract Content
LB-A001 R/R DLL3-high extrapulmonary neuroendocrine carcinoma
LB-A003 Efficacy and safety in EP-NEC with high or low DLL3 expression (presenting author reported as Tim Remus, Boehringer Ingelheim — attribution from a search snippet, not primary-verified)
LB-A004 DAREON-7 — Phase I dose escalation/expansion, first-line obrixtamig + chemotherapy
LB-A005 DAREON-8 — Phase I, first-line obrixtamig + chemotherapy + atezolizumab in ES-SCLC
LB-A002 Separate BI asset: BI 765179 (CD137/FAP agonist) + pembrolizumab, open-label Phase Ib dose expansion, first line

The strategically interesting one is LB-A003: extending into low DLL3 expressers is an argument that the target threshold is lower than assumed, which would materially expand the addressable population. Watch whether it survives a randomized setting.

CART19/20 — bispecific CAR-T in non-Hodgkin lymphoma

  • Abstract LB-C001 — "Phase 1 Trial of Bispecific CART19/20 Cells for Relapsed or Refractory Non-Hodgkin Lymphoma: Updated Results with Over Four Years Median Follow Up" (UCLA)
  • Presenting author reported as Sophie Carlson (UCLA) — attribution from a search snippet, not primary-verified

"Over four years median follow-up" is the finding. Durability data at that horizon in a Phase 1 CAR-T cohort is rare and is worth more than most first-report response rates. The bispecific CD19/CD20 design directly targets antigen-escape relapse, and four years is long enough to say something real about whether it works.

NIBIT-ML1 — epigenetic reprogramming to overcome PD-1 resistance

  • Abstract LB-C004 — "Epigenetic immune reprogramming overcomes PD-1 resistance in metastatic melanoma patients: the phase II NIBIT-ML1 study" (University of Siena / NIBIT, Italy); reported presenter Anna Maria Di Giacomo
  • Companion: LB-C009 — NIBIT-EPI-MESO, methylation subtypes predicting IO outcome in pleural mesothelioma

Cross-meeting note: the same study was re-presented at the AACR Annual Meeting 2026 as abstract CT236 (Cancer Research vol 86, 8_Supplement). This is one of the few cases where the corpus can follow a single study across two meetings two months apart — a useful test case for how presentation framing shifts between an IO-specialist audience and a general oncology one. See aacr-2026/topics/clinical-trials/.

A clean negative result — chronotherapy in adjuvant melanoma

  • Abstract LB-B005 — adjuvant pembrolizumab, NCI/SWOG resectable melanoma: "No effect of the time-of-day infusion" on outcomes.

Worth flagging on its own. Time-of-day effects on immunotherapy have generated a run of positive retrospective reports; a null result from a cooperative-group trial population is the kind of finding that rarely gets amplified and should be. File alongside the negative-result material in PSB 2026 as evidence the corpus tracks refutations, not just claims.

Other named agents and platforms

Agent / platform Abstract Notes
Pepinemab LB-C007 SEMA4D-blocking antibody
SVV-001 LB-B002 Oncolytic virus + nivolumab + ipilimumab, Phase 1, high-grade neuroendocrine neoplasms
AGB201 B063 First-in-class LTβR × EDB bispecific inducing tertiary lymphoid structures
Cadonilimab LB-B004 Neoadjuvant; CD8 TIL + systemic immune-inflammation index as response predictor
Metronomic gem/dox/docetaxel + nivolumab LB-B006 Phase II, advanced angiosarcoma
Flare LB-C010 Delivery platform
RedTail LB-C005 Systemic BiTE delivery
DN64-CAR-V LB-B011 Amphotropic RNA vector for in vivo CAR generation

The autoimmunity readout — CAR-Tregs in rheumatoid arthritis

Presented in Fred Ramsdell's closing-day keynote rather than as an abstract. Phase I, 9 patients with severe refractory RA, no adverse events reported, synovial inflammation reduced by week four. Full detail on the keynotes page.

Caveats

  • Presenter attributions for LB-C001 and LB-A003 came from search snippets rather than primary reads of the abstracts. Verify against Crossref before citing.
  • OncLive and BioWorld coverage is paywalled or Cloudflare-blocked; no trade-press body text was read for this page.
  • No AACR press-program release exists for this meeting — unusual for an AACR conference, and it means there is no official curated "top abstracts" list to check this selection against.

Sources