zoldonrasib

Zoldonrasib (RMC-9805) is Revolution Medicines' oral, G12D-selective RAS(ON) inhibitor - the first drug of its kind to enter Phase 3 [1][2]. KRAS G12D is the single most common cancer-driving mutation in pancreatic adenocarcinoma (PDAC), present in roughly 40% of cases, and a meaningful slice of colorectal cancer and NSCLC [8]. RASolute 305, a randomized Phase 3 in first-line metastatic G12D PDAC adding zoldonrasib to investigator's-choice chemotherapy versus placebo plus the same chemo backbone, started enrolling in 2026 with a 670-patient target [2]. If the add-on combination works, this is the first targeted therapy for a disease where standard chemo delivers median survival under a year. The FDA granted Breakthrough Therapy Designation for the NSCLC G12D indication in 2026 on the strength of a 61% ORR in 18 evaluable Phase 1 patients at the 1200 mg QD recommended dose [9][10].

Zoldonrasib is a novel small molecule, never approved anywhere. It moved from first-in-human Phase 1 (RMC-9805-001, NCT06040541) into Phase 3 on the strength of monotherapy and combination response signals presented across 2025-2026 [3][4][11]. In the NSCLC monotherapy cohort at 1200 mg QD (the recommended Phase 2 dose), Revolution reported a 61% ORR, 89% disease control rate, and median time-to-response of 1.4 months in 18 evaluable patients [9][10]. In the PDAC + mFOLFIRINOX combination cohort, first-line patients showed ORR in the 53-63% range across 19 evaluable patients - a striking signal in a tumor type where chemo alone delivers ORR in the 20-30s [3][4]. On the strength of the NSCLC monotherapy data, the FDA granted Breakthrough Therapy Designation in 2026 for KRAS G12D-mutated NSCLC in patients previously treated with anti-PD-(L)1 plus platinum chemo [9][10]. Orphan drug designation status has not been publicly confirmed as of mid-2026; the PDAC setting makes it likely but should not be assumed. The Phase 3 RASolute 305 add-on combination program is recruiting [2], and a parallel Phase 1 with Akeso/Summit's PD-1/VEGF bispecific ivonescimab opened in early 2026 [5]. First Phase 3 PFS readout is plausibly 2027, with an earlier interim possible.

KRAS is a protein that acts like an on/off switch for cell growth. Mutations at position 12 - G12C, G12D, G12V - jam the switch in the 'on' position, so cells divide when they shouldn't. G12D swaps glycine for aspartate, which is the most common KRAS mutation overall but has no chemical 'handle' that earlier G12C drugs (sotorasib, adagrasib) could grab onto. That's why G12D resisted drugging for decades. Revolution's trick is the RAS(ON) tri-complex approach: zoldonrasib binds cyclophilin A, a common cellular protein, and the resulting complex slots into the active (GTP-bound) form of KRAS G12D, blocking it from talking to downstream effectors like RAF [6]. This is mechanistically different from the G12C drugs, which only bind the inactive state. Validation comes from three places: human genetics (G12D drives the tumor - knock it out in models and tumors regress), the success of G12C inhibitors as proof RAS is druggable, and zoldonrasib's own Phase 1 monotherapy responses in tumor types where targeted single agents almost never work [1][9].

RASolute 305 (NCT07621718) is a randomized Phase 3 in first-line metastatic KRAS G12D-mutated PDAC, comparing zoldonrasib plus investigator's-choice chemotherapy versus placebo plus the same chemo backbone [2]. Primary endpoint is progression-free survival (PFS), with overall survival as a key secondary. Target enrollment is 670 patients, sponsor is Revolution Medicines, status is recruiting as of 2026. Letting investigators choose the chemo backbone (likely mFOLFIRINOX or gem/nab-paclitaxel) is pragmatic - it mirrors real-world prescribing and avoids locking the trial to a single regimen, though it adds heterogeneity to interpret. PFS as primary is appropriate for PDAC, where OS is confounded by post-progression therapy. The parallel Phase 1 (NCT07397338) is testing RAS(ON) inhibitors including zoldonrasib combined with ivonescimab (PD-1/VEGF bispecific) in 370 solid tumor patients, primary endpoint is safety [5]. The big design question is whether adding zoldonrasib to chemo gives enough of a PFS bump to clear the bar - the Phase 1 PDAC + mFOLFIRINOX ORR of 53-63% suggests the combination is biologically active; whether that translates to PFS magnitude in a randomized setting is the unknown.

Our model gives this drug a 17% chance of eventually being approved. That number starts from the historical approval rate for Phase 3 drugs in this area - about 48% - then adjusts based on ten specific facts about the trial and sponsor. The estimate is helped by an above-average number of secondary endpoints, but pulled down by the sponsor's weak approval track record and limited earlier-phase results. The remaining factors are typical for this stage, so they leave the final number close to where those key adjustments put it.

Efficacy risk is the biggest. Single-agent G12D inhibition has shown striking Phase 1 responses, but durability is the open question - resistance mechanisms in KRAS-driven tumors emerge fast. The G12C class is the predictive precedent: sotorasib and adagrasib generate responses but median PFS lands at 6-7 months, with resistance via secondary KRAS mutations, MAPK reactivation, MET amplification, and RTK feedback. G12D is unlikely to escape this pattern. The placebo+chemo control arm in RASolute 305 will get standard chemo, which sets a moving target since chemo combinations have improved modestly over the last decade. Safety risk includes on-target effects of RAS pathway inhibition - rash, GI toxicity, fatigue have been the dominant Phase 1 adverse events for the RAS(ON) class, and adding chemo will stack toxicity. Cyclophilin A binding is novel and could produce off-target effects no one has seen at chronic dosing yet. Execution risk is real: enrolling 670 G12D-positive PDAC patients globally requires aggressive screening since not every PDAC patient gets sequenced. Competition for the same population is intensifying: BMS/Mirati's MRTX1133 is a non-covalent G12D inhibitor in Phase 1/2 with delivery challenges; Astellas' ASP3082 is a Phase 1 G12D-targeted protein degrader; Hengrui's HRS-4642 is a Phase 1 covalent G12D inhibitor primarily developed in China. Platform risk: Revolution's own daraxonrasib (RMC-6236, pan-RAS) shares the tri-complex mechanism - a tri-complex-specific safety signal would hit both programs simultaneously. Commercial risk is lower than typical - if zoldonrasib hits PFS, payers will cover it in a disease this lethal.

Worth watching closely - the program has already cleared key derisking milestones. Zoldonrasib is the most advanced G12D-selective program in clinical development, FDA-designated BTD in NSCLC, and the Phase 1 ORR data (61% NSCLC monotherapy, 53-63% PDAC + chemo) are substantially above the typical >20% threshold investors would expect from a credible Phase 3 candidate - the bar that matters now is durability, not response rate [9][3][4]. The signals to watch: median duration of response and PFS from Phase 1 expansion updates at ASCO 2026 or ESMO 2026, and whether DoR pushes past six months in pretreated patients. Check back at the next 8-K following a major medical meeting [3][4]. Also watch RMC-6236 (daraxonrasib) Phase 3 readouts - but recognize daraxonrasib is Revolution's own pan-RAS program, not a competitor; positive data there derisks the entire tri-complex platform and pulls zoldonrasib's odds up with it, while a tri-complex safety signal would hit both. Revolution's cash position has historically been strong (multi-year runway maintained through 2024-2025 partnered and equity financings), but the company is oncology-only and pre-revenue; one bad readout moves the stock hard. The true competitive set is MRTX1133 (BMS/Mirati, Phase 1/2), ASP3082 (Astellas, Phase 1), and HRS-4642 (Hengrui, Phase 1) - all behind zoldonrasib in clinical stage. For investors, zoldonrasib is the lead asset in a franchise where the platform itself is the bet.