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Preprint WatchModerateSeptember 18th, 2026

A directed TM->JM coupling in receptor tyrosine kinase dimers, set by activating mutations and the membrane environment

Sato, T.; Tamagaki-Asahina, H.

Molecular dynamics of transmembrane and juxtamembrane dimers indicates that the direction of conformational coupling in EGFR and FGFR3 is set by activating transmembrane mutations and by the membrane environment, with activating mutants EGFR L658Q and FGFR3 A391E altering the transmembrane to juxtamembrane directed-mass fraction.

Moderate contradiction

2 prior failures

Two documented clinical failures match this mechanism, or a single Phase 3 failure is on record.

The preprint argues that activation in EGFR and FGFR3 dimers has a direction, running from the transmembrane segment to the juxtamembrane region, and that activating transmembrane mutations and lipid environment set it. Claidex holds two EGFR claims, both in EGFR mutation-positive non-small cell lung carcinoma. One failed on tumour uptake and dosimetry rather than on target biology (fpi-2107-egfr-cmet-nsclc-dosimetry-uptake-failure) and one was shut down for sponsor reasons (bg-60366-egfr-cdac-nsclc-strategic-shutdown). FGFR3 carries a third relevant claim, a Phase 2 achondroplasia program terminated by sponsor decision (sar442501-fgfr3-achondroplasia-phase2-sponsor-termination). The work is computational and structural, with no efficacy or exposure data, so it neither supports nor contradicts those terminations. It is recorded because it proposes a membrane-dependent activation mechanism for two targets whose recent clinical failures in this graph were driven by delivery and portfolio decisions, where a membrane-context-dependent conformational state would be a plausible place to look next rather than an established one.

Abstract excerpt

The direction of conformational coupling in a membrane protein, that is, which domain drives which, has been inaccessible to experiment. We recover this directivity from molecular dynamics (MD) of transmembrane-juxtamembrane (TM-JM) dimers of receptor tyrosine kinases EGFR and FGFR3. Coupling is detected with a Bayesian-network framework (CASCADE); its direction is measured with PERI (Phase-plane Estimation of Rotational Irreversibility), the net phase-plane circulation, validated on synthetic data and resolved at 0.1 ns. Direction is summarized as the TM[->]JM directed-mass fraction f+ (0.5 = balanced) via a hierarchical Bayesian model. The activating TM mutants EGFR L658Q and FGFR3 A391E are TM-JM (posterior probability 0.95 and 0.99); fluid wild-type EGFR leans the same way (0.93), in agreement with its experimentally reported constitutive activity in fluid but not ordered bilayers; the ligand-dependent ordered wild type is balanced (0.45); and an activating mutation raises the TM-JM bias above the ordered wild type with probability 0.94. The directivity thus tracks the measured activity state of the receptor, distinguishing signaling-competent from ligand-dependent RTK dimers by a property not apparent from structure alone.

Matching Claidex post-mortems

2 of 2 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.