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Preprint WatchMildSeptember 26th, 2026

A Rationally Designed Transgene Drives CAR T Functional Persistence and Durable Regression of Solid Tumors

Amin RH, Haworth KG, Moffett HF, Chen JC, Park L, Yokoyama JK, Wang AL, Tait LJ, Steele MM, Crowl JT, Davenport TM, DeSautelle J, Hammer JL, Obenza WM, Montoya VR, Kirkpatrick RL, Tan T, Shirley KM, Hammerson B, Langan RA, Clausen DS, Sample PJ, Weitzner BD, Yuan S, Lajoie MJ, Boyken SE, Foster AE.

A single-vector transgene combining a high-avidity mesothelin CAR designed to resist shed decoy antigen, an activation-responsive promoter, a CD8-targeted IL-2 and an EGFR safety switch eradicates established solid tumors at low CAR T doses in mouse models.

Mild contradiction

1 prior failure

One documented clinical failure (Phase 1 or 2) overlaps with the claimed mechanism.

This preprint reports a four-component engineered CAR T construct against mesothelin that clears established lung and ovarian tumors in mouse models at low cell doses. Claidex holds one prior MSLN failure, sgn-mesoc2-msln-mesothelin-adc-solid-tumors-phase1-strategic-termination, where the SGN-MesoC2 antibody drug conjugate program was terminated in Phase 1 for strategic reasons. The modalities are different and the prior stop was not an efficacy readout, so this is a watch item rather than a contradiction. Two features of the preprint do engage the historical failure mode for this target. Shed soluble mesothelin is explicitly designed around, which is the antigen-sink problem that has limited MSLN-directed agents, and the efficacy claim rests on mouse xenograft models, where mesothelin expression in normal tissue does not mirror the human safety margin. Severity is MILD because the single matching claim is a strategic termination.

Abstract excerpt

The eradication of solid tumors by chimeric antigen receptor (CAR) T cells requires dynamic therapies capable of outlasting an immune suppressive tumor microenvironment (TME). However, biological barriers—including rapid exhaustion, poor expansion, and loss of stem-like memory—quickly neutralize these therapies. Because single-technology interventions often introduce unacceptable tradeoffs between efficacy and safety, durable remission demands a paradigm where multiple engineered solutions work in concert. To holistically address these mechanisms, we rationally designed a single-vector transgene that intrinsically drives CAR T functional persistence. The platform integrates four synergistic technologies: a high-avidity mesothelin (MSLN)-targeting CAR optimized to resist shed decoy antigens, a T-cell activation-responsive promoter (OUTLAST OP1) resisting exhaustion, a CD8α-targeted designed IL-2 cytokine (OUTSMART dIL-2) driving intratumoral CAR-T expansion, and an EGFRopt safety switch. In lung and ovarian cancer models, this rational integration was required to drive antigen-dependent T cell expansion and eradicate established tumors at extremely low CAR T doses. Furthermore, engineered cells established a self-renewing pool of stem-like memory T cells capable of rejecting tumor rechallenge months later. Ultimately, this work demonstrates that intrinsic T cell dysfunction and

Matching Claidex post-mortems

1 of 1 indexed

This is an automated contradiction flag, not an editorial judgment on the preprint's quality. Flags identify where the preclinical literature and the clinical failure record diverge.