Material Event (Form 8-K)

Other Events.

Pharmacokinetics (PK) in AURORAS-1:

Well-behaved PK, with dose-dependent increase in PK exposure up to the maximum administered dose (MAD) of 40 mg once daily (QD) and no exposure plateau observed.

Pharmacologically active dose (PAD) range of 16-32 mg QD defined based on mean steady-state average exposures that exceeded target exposure threshold (based on the insensitive xenograft model).

Pharmacodynamics (PD) in AURORAS-1:

Substantial reductions in KRAS G12X circulating tumor DNA (ctDNA) were observed at the PAD doses (16-32 mg QD), with 100% of patients (14/14) showing at least 75% reduction in KRAS G12X variant allele fraction, including 5 out of 14 patients showing 100% reduction.

Efficacy in AURORAS-1 and JYP0015M101 trials: Robust monotherapy overall response rates (ORR) in patients with KRAS G12X non-small cell lung cancer (NSCLC) and with KRAS G12X pancreatic cancer (PDAC), in each case as of the relevant data cut off (DCO)^1,2:

NSCLC

At PADs of 16-32 mg QD, 62% uORR_8wk (N=37) in second line or greater (2L+) KRAS G12X NSCLC, which exceeded comparator by 24 percentage points^3,4

At PADs of 16-32 mg QD, 75% uORR_8wk (N=16) in post-ICI/platinum (2/3L) KRAS G12X NSCLC, which exceeded comparator by 37 percentage points^3,4

At recommended doses for expansion (RDEs) of 24-32 mg QD, 64% uORR_8wk (N=25) in 2L+ KRAS G12X NSCLC³

PDAC

At PADs of 16-32 mg QD, 40% uORR_14wk (N=20) in 2L KRAS G12X PDAC, which exceeded comparator by 11 percentage points^5,6

At RDEs of 24-32 mg QD, 42% uORR_14wk (N=12) in 2L KRAS G12X PDAC, which exceeded comparator by 13 percentage points^5,6

At RDE of 32 mg QD, 50% uORR_14wk (N=2) in 2L KRAS G12X PDAC, which exceeded comparator by 15 percentage points^5,7

Multiple ongoing responses: Nearly all responding patients-including all unconfirmed responders-remain on treatment as of the DCO:

NSCLC

23 out of 24 responding patients remain on treatment, including all responders treated at 24-32 mg QD RDEs

PDAC

20 out of 23 responding patients remain on treatment, including all responders treated at 24-32 mg QD RDEs

Safety and Tolerability: Generally well-tolerated with mostly low-grade adverse events (AEs), no dose-limiting toxicities (DLTs), low rate of dose interruptions or reductions due to treatment-related adverse events (TRAEs), and no discontinuations due to TRAEs

Monotherapy RDE: Based on the totality of the preliminary Phase 1 dose escalation data, 24 mg and 32 mg QD were selected as the go-forward monotherapy RDEs

Combinability: ERAS-0015 showed promising clinical potential to combine with panitumumab (anti-EGFR monoclonal antibody)

No DLTs observed through the 31Mar2026 DCO (N=3) with 1 uPR in 1 efficacy-evaluable patient with metastatic colorectal cancer (CRC)

AURORAS-1 data cutoff (DCO) 4Apr2026; JYP0015M101 DCO 27Feb2026

Pooled data from the Company's Phase 1 trial (US trial, or AURORAS-1) and Joyo's Phase 1 trial (China (CN) trial, or JYP0015M101) of ERAS-0015

The uORR_8wk is the ORR (confirmed and unconfirmed responses) for patients who received first dose of ERAS-0015 at least 8 weeks prior to DCO (US trial) or at least one post-dose tumor assessment (CN trial)

Comparator as used in this report, RMC-6236. Punekar et al. Journal of Thoracic Oncology 2025; DCO 30Sep2024

The uORR_14wk is the ORR (confirmed and unconfirmed responses) for patients who received first dose of ERAS-0015 (US, CN) at least 14 weeks prior to DCO

Wolpin et al. EORTC-NCI-AACR 2024; DCO 23Jul2024

Revolution Medicines Press Release (10Sep2025); DCO 30Jun2025

One Grade 3 TRAE of pneumonitis progressed to Grade 5 after withdrawal of supportive care per patient decision. The patient was a 66 year-old male with heavily pretreated metastatic pancreatic adenocarcinoma who received 24 mg of ERAS-0015. The patient had pulmonary metastases, a history of right lung cryoablation and no history of lung radiation. The patient presented to the ER approximately a month after starting ERAS-0015 with Grade 3 pneumonitis that was treated aggressively with immediate discontinuation of ERAS-0015, high dose steroids and infliximab. The patient requested withdrawal of supportive care and ultimately died of the event.

Rash events are identified using following preferred term rash pustular, rash papular, rash maculo-papular, rash macular, rash, erythema and dermatitis acneiform (uncoded terms rash acneiform and rash, are also included).

2 and 8 mg cohorts did not enroll patients with NSCLC.

Safety analysis set: all patients with PDAC or NSCLC that received at least one dose of ERAS-0015.

2 and 4 mg cohorts did not enroll patients with NSCLC.

AURORAS-1 Phase 1 trial for ERAS-0015 (pan-RAS molecular glue) in patients with RAS-mutant solid tumors:

Monotherapy expansion data and combination dose escalation data narrowed to an expected date of first half of 2027.

BOREALIS-1 Phase 1 trial for ERAS-4001 (pan-KRAS inhibitor) in patients with KRAS-mutant solid tumors:

Preliminary Phase 1 monotherapy data expected in the second half of 2026.

Initiation of monotherapy expansion cohorts and combination dose escalation cohorts planned for 2027.