# Figure 1 mechanism audit

Checked 2026-09-07 against primary regulatory, experimental and structural sources. Panel text below is authored paraphrase, not source quotations. Figures describe mechanisms, not quantitative simulations or predictions of patient response.

## T-DM1 — HER2-positive breast cancer

1. **Delivery to the tumor.** Intravenous T-DM1 circulates in blood; a fraction reaches tumor tissue. Show a vessel, surrounding matrix and several unbound conjugates rather than every particle reaching a cell.
2. **HER2 recognition.** Trastuzumab binds HER2 on the cancer-cell surface. Magnify the antibody–receptor contact and show the attached DM1 payloads.
3. **Cellular uptake.** The bound conjugate enters the cell through receptor-mediated internalization. Retain the membrane, endosomal compartment and cell outline.
4. **Lysosomal processing.** Proteolysis of the antibody releases DM1-containing catabolites, including lysine–MCC–DM1. Show the noncleavable linker remaining attached to the catabolite, not snapping off as free DM1.
5. **Microtubule disruption.** Active catabolites reach the cytosol; DM1 activity disrupts the microtubule network. Show tubulin and a disrupted mitotic spindle within the same cell.
6. **Cell-cycle arrest and death.** Microtubule disruption can lead to cell-cycle arrest and apoptosis. Show affected and surviving cells; do not imply uniform tumor eradication.

Sources:
- KADCYLA US prescribing information, sections 11 and 12.1: https://www.gene.com/download/pdf/kadcyla_prescribing.pdf
- EMA original assessment, mechanistic catabolite description: https://www.ema.europa.eu/en/documents/assessment-report/kadcyla-epar-public-assessment-report_en.pdf
- Primary experimental study of SLC46A3/catabolite transport: https://pmc.ncbi.nlm.nih.gov/articles/PMC9896951/

Boundaries: vessel crossing is a conceptual delivery context, not a validated T-DM1 extravasation rate or a literal fixed route. No numerical delivery fraction is justified here. Intracellular lysosomal processing must separate membrane binding from tubulin action. The antibody also retains HER2 signaling inhibition and ADCC activity (label in vitro evidence); these are supplementary mechanisms, not a reason to omit payload processing. Do not portray a strong freely diffusing bystander field as the core T-DM1 mechanism.

## Tisagenlecleucel — relapsed/refractory B-cell ALL

1. **Collect and engineer T cells.** Patient T cells are collected and modified outside the body to express a CD19-directed CAR. Show collection, gene transfer and expansion; do not depict engineering inside the patient.
2. **Return the cells.** After lymphodepleting chemotherapy, CAR T cells are infused. Show blood and marrow context rather than a solid-tumor mass for this ALL case.
3. **Recognize CD19.** CAR T cells contact CD19-expressing leukemia cells. Magnify CAR–CD19 binding across two distinct cell membranes.
4. **Activate the T cell.** CD3-zeta initiates activation; 4-1BB supports expansion and persistence. Show these signaling domains on the cytoplasmic side of the CAR T membrane.
5. **Deliver the killing signal.** Cytotoxic granules move toward the cell–cell contact and release their contents. Show localized release toward the target, followed by target-cell apoptosis.
6. **Expand and persist.** CAR T cells can expand and persist after infusion. Normal CD19-positive B cells can also be depleted; persistence does not guarantee durable response.

Sources:
- KYMRIAH US prescribing information, sections 2, 11, 12.1–12.3: https://www.novartis.com/us-en/sites/novartis_us/files/kymriah.pdf
- Primary experimental CAR synapse study: Davenport et al., PNAS 2018, doi:10.1073/pnas.1716266115; https://pmc.ncbi.nlm.nih.gov/articles/PMC5834689/ (search indexed primary article; full PMC open encountered browser challenge).

Boundaries: granule/synapse detail is a general experimental CAR-T mechanism, not a product-specific movie of KYMRIAH. CAR synapses are not necessarily a perfect textbook concentric bullseye. Retain both cells and their contact while magnifying. Avoid depicting cancer-only CD19 specificity. The label supports normal-cell elimination, expected B-cell aplasia, and activation/expansion/persistence. Clinical percentages belong on the evidence page, with the relevant cohort and follow-up.

## Daraxonrasib — pancreatic ductal adenocarcinoma

1. **Locate the disease.** Begin with pancreatic tumor tissue and its surrounding stroma and vessels. Show the tumor-cell compartment that will remain visible through later magnifications.
2. **Enter the cell.** Oral daraxonrasib reaches cells through systemic exposure. Show the small molecule in the cytosol; avoid an antibody-style receptor uptake or an endosome-to-lysosome route.
3. **Recruit cyclophilin A.** Daraxonrasib associates with intracellular cyclophilin A (CypA), creating a drug–protein complex.
4. **Engage active RAS.** The complex binds GTP-bound RAS at the inner cell membrane. Show the CypA–daraxonrasib–RAS tri-complex, with the membrane retained in the wider scene.
5. **Block effector access.** The tri-complex obstructs RAS effector binding, suppressing downstream signaling. Show an approaching RAF effector excluded from RAS and reduced RAF–MEK–ERK signaling.
6. **Reduce growth signaling.** RAS inhibition can reduce tumor-cell proliferation and survival. Show cell-level consequences without implying that all tumor cells die or that the molecular animation predicts the trial response.

Sources:
- Jiang et al., Cancer Discovery 2024, primary translational RMC-6236 study: https://pmc.ncbi.nlm.nih.gov/articles/PMC11149917/ ; doi:10.1158/2159-8290.CD-24-0027
- Cregg et al., J Med Chem 2025, discovery/structural primary study: https://doi.org/10.1021/acs.jmedchem.4c02314
- Experimental coordinates: https://www.rcsb.org/structure/9BG6 (1.66 angstrom X-ray structure, KRAS G12V + CypA + daraxonrasib; nucleotide is GNP, a GTP analogue).
- Manufacturer MOA page: https://hcp.rasonque.com/ras-on/moa (primary sponsor information supports tri-complex, effector exclusion and downstream signaling inhibition).
- FDA current approval announcement: https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-daraxonrasib-metastatic-pancreatic-adenocarcinoma (August 26, 2026; metastatic pancreatic adenocarcinoma; current FDA page retrieved). Full RASONQUE label was not independently retrieved in this bounded audit; do not claim its section 12.1 was inspected.

### GTP hydrolysis: supported but must be qualified

The primary Nature study **Pharmacological restoration of GTP hydrolysis by mutant RAS**, Nature 637, 224–229 (2025), https://www.nature.com/articles/s41586-024-08283-2 , reports CypA-bound RMC-6236 stimulated KRAS G12D GTP hydrolysis similarly to RMC-7977 (Extended Data Fig. 4a,b). This is real preclinical support, not an invented mechanism. However, it is variant-dependent and does not establish uniform hydrolysis restoration across all RAS mutations or quantify its contribution to patient benefit. Search retrieved this exact experimental result; full article text retrieval was intermittently unavailable.

Recommendation: keep **effector blockade** as main panel 5. If hydrolysis is added as a molecular inset, caption: **“Preclinical studies also show enhanced GTP hydrolysis in some RAS variants.”** Cite the Nature study. Do not show all RAS molecules switching OFF, mutation repair, irreversible binding, or a guaranteed shutdown. Do not use 9BG6 itself as evidence of hydrolysis: it captures a static G12V complex with a nonhydrolyzable nucleotide analogue. A G12D-specific depiction can instead cite/inspect PDB 9AX6 mentioned in the Jiang paper before using its coordinates.

## Shared visual rules

- Use six connected panels with short labels, one color per therapy component and retained anatomical context.
- Microscopic scenes, arrows and transit times are explanatory compositions; no invented distance, speed, concentration or response percentage.
- Separate molecular mechanism from clinical outcomes and safety. Include a concise legend noting scale/time compression, rather than cluttering every panel.
- Do not call Figure 1 a methods validation figure: it is a mechanism figure. Explain how the artwork was constructed and sourced in the legend if useful.