Three new angles on cancer's oldest trick: resisting the therapy
In preprints posted this week, researchers map isoform-selective antibody-drug binders, a tractable mouse model of tertiary lymphoid structures, and a chromatin complex driving AR-V7 in prostate cancer.
- In a preprint, VHH-Fc binders engineered against B7-H3's membrane-proximal domain pair show 10–100x higher affinity for the 4Ig isoform than the 2Ig isoform; clinical antibodies ifinatamab, mirzotamab, and vobramitamab do not discriminate between isoforms. Self-reported m:…6945
- In the same preprint, internalization efficiency of B7-H3 binders is reported to be independent of binding affinity and epitope location — a separate ADC design variable. Self-reported m:…6945
- In a preprint, researchers report CXCL9 is a key regulator of the tertiary lymphoid structure microenvironment and is required for B cell recruitment to peritumoral tissue; anti-PD-L1 treatment induces TLS expansion and tumor clearance, and the subcutaneous murine TLS model's immune composition resembles human cancer TLS signatures. Self-reported m:…2521
- In a preprint, the cBAF chromatin remodeling complex is reported to drive AR-V7 expression in castration-resistant prostate cancer cells: cBAF-dependent transcriptional termination is required for AR-V7 biogenesis, and cBAF loss reduces RNA polymerase II Thr4 phosphorylation and promotes readthrough beyond the AR-V7 polyadenylation site. Self-reported m:…8128
Isoform-selective binders for B7-H3 ADCs
Antibody-drug conjugates live or die on selectivity: the antibody must carry its toxic payload to the tumor's version of a target and spare the rest. In a preprint posted this week, researchers describe VHH-Fc binders engineered against the membrane-proximal domain pair of B7-H3 that show 10- to 100-fold higher affinity for the 4Ig isoform than for the 2Ig isoform — selectivity built on epitope geometry rather than raw binding strength. m:…6945
The contrast that matters: clinical-stage antibodies ifinatamab, mirzotamab, and vobramitamab do not discriminate between B7-H3 isoforms, the researchers report. If isoform selectivity translates to a wider therapeutic window, today's B7-H3 ADC programs are leaving selectivity on the table — hitting both isoforms wherever they appear. m:…6945
A second design variable emerges from the same paper: internalization efficiency — how well the cell takes up the binder — is independent of binding affinity and epitope location. That decouples two things ADC developers often assume travel together: a tighter binder is not automatically a better-internalizing one, so optimizing for affinity alone can mean optimizing for the wrong variable. m:…6945
A tractable TLS model
Tertiary lymphoid structures are organized immune formations that arise inside or near tumors — local hubs where B cells and T cells organize. They are hard to study in mice. A second preprint, published on bioRxiv, introduces a subcutaneous murine tumor model that naturally develops TLS within peritumoral adipose tissue, and reports that its immune composition resembles human cancer TLS signatures. m:…2521
The researchers identify CXCL9 as a key regulator of the TLS microenvironment, required for B cell recruitment to peritumoral tissue. They also report that anti-PD-L1 treatment induces TLS expansion and tumor clearance, associated with increased interferon responses in macrophages — a named regulator and a combination lever, in one model. m:…2521
For anyone screening immunotherapy combinations, the model is the deliverable: a tractable system whose TLS look human-like, paired with a regulator to perturb. Checkpoint-blockade resistance is often a microenvironment problem, and this gives researchers a knob to turn in the exact compartment where that resistance lives. m:…2521
A new driver of AR-V7
A third preprint, on bioRxiv, names a driver of AR-V7 expression in castration-resistant prostate cancer: the cBAF chromatin remodeling complex. The researchers report that cBAF-dependent transcriptional termination is required for AR-V7 biogenesis in CRPC cells. m:…8128
The mechanism sits at the level of the transcription machinery itself. cBAF binds an intronic regulatory element downstream of AR cryptic exon 3, maintaining chromatin accessibility and promoter-enhancer looping. When cBAF is lost, RNA polymerase II Thr4 phosphorylation drops and transcription reads through beyond the AR-V7 polyadenylation site — producing the truncated variant transcript that lets the cancer escape androgen-directed pressure. m:…8128
That makes cBAF a candidate target upstream of the variant itself — disrupting the termination machinery that produces AR-V7 rather than chasing the variant. It is early, and preprints are not evidence of druggability — but the mechanism is specific enough to test. m:…8128
One thread: resistance has an address
Put the three together and the week's thread is clear: therapy resistance is not one phenomenon but a set of addressed, testable mechanisms — a target hidden behind isoform diversity, an immune microenvironment lacking organizing structure, a transcription termination program that manufactures a resistance variant. m:…6945 m:…2521 m:…8128
And each mechanism arrives with a counter-move attached: an isoform-selective binder design, a tractable TLS model with a named regulator, a chromatin complex whose disruption blocks the variant's production. For investors, that is the shape of the diligence question this week — not whether resistance exists, but whether a program has named its address and brought a way to reach it. m:…6945 m:…2521 m:…8128
What is still unresolved
- All three are preprints; results come from the authors' own experiments and have not been independently reproduced.
- The B7-H3 binders were characterized as binders; the study does not report full ADC constructs tested for efficacy.
- The TLS model is murine; translation to human tumors is unproven.
- cBAF disruption was characterized in CRPC cells; the study reports no in vivo or therapeutic data.
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