Mythic Therapeutics Presents Compelling Efficacy Data from its Phase 1 KisMET-01 Study Supporting Best-in-Class Potential of Novel cMET- ADC, MYTX-011, in Non-Small Cell Lung Cancer at the American Society of Clinical Oncology (ASCO) Annual Meeting

Initial efficacy data for Mythic’s pH-engineered cMET-directed antibody-drug conjugate (ADC) demonstrates meaningful anti-tumor activity across all cMET expression levels, histologies, and actionable genetic alterations

Preliminary overall response rate (ORR) of 36% in patients with cMET low tumors, 39% in patients with cMET high tumors and 50% in tumors with EGFR mutations and cMET high/intermediate levels, with response durations of up to 8.9 months observed

Preliminary data suggest the potential for MYTX-011 to address the high unmet need in the up to 60% of previously treated patients with NSCLC whose tumors have progressed after prior therapies

Mythic Therapeutics, a clinical-stage biotechnology company developing next-generation antibody-drug conjugate (ADC) therapies for the treatment of a wide range of cancers, today presented updated data from its Phase 1 KisMET-01 study evaluating its investigational cMET-targeting ADC candidate, MYTX-011, in patients with previously treated, locally advanced or metastatic non-small cell lung cancer (NSCLC), in a poster at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting. MYTX-011 is a novel ADC engineered with pH-dependent binding to more precisely deliver anti-tumor payload across a range of cMET expression levels, with the goal of reducing toxicity and expanding the number of patients who can benefit from ADC therapy.

“We are highly encouraged by these early efficacy data demonstrating meaningful anti-tumor activity which underscore how our differentiated pH-dependent design may help unlock the full promise of ADCs to reshape cancer treatment and expand patient reach, regardless of histology and molecular subtype,” said George Eliades, Ph.D., President and Chief Executive Officer at Mythic Therapeutics. “Together with a manageable tolerability profile, these findings support the potential of MYTX-011 to establish a new standard of care for pretreated NSCLC patients in second- and later-line settings, where effective treatment options remain extremely limited. We look forward to evaluating MYTX-011 in Part 2 of the study and plan to present updated expansion cohort data at an upcoming medical conference.”

Data presented were from 66 patients treated at efficacious dose levels (≥4.0 mg/kg) administered once every three weeks (Q3W) in Part 1 of the dose escalation portion of the study. Patients had a median of three, and up to 10, prior lines of therapy with nearly half (45%) receiving prior taxane treatments. Preliminary results show:

• Anti-tumor activity was consistent regardless of cMET expression levels, EGFR mutation status or prior taxane treatment.
  • In non-squamous, cMET+ tumors, the ORR was 39% in cMET high/intermediate (n=23) and 36% in cMET low tumors (n=11).
  • Responses were observed in patients with and without actionable genomic alterations, including a 50% ORR in patients with tumors containing both EGFR mutations and cMET high or intermediate expression.
• Overall, responses were durable, with observed durations of up to 8.9 months and ongoing; the majority of patients with responses remain on treatment.
• Disease control rate (DCR) was 80% at 12 weeks (n=24 of 30) and 52% at 24 weeks (n=14 of 27).
• All four response-evaluable patients with squamous histology tumors and low cMET levels had clinical benefit; one partial response was observed and the three other patients had durable stable disease.

MTYX-011 demonstrated favorable pharmacokinetics (PK) and excellent stability. The overall safety profile of MYTX-011 was consistent with previously reported data, and no new safety signals were identified. The most common treatment-related adverse events (TRAEs) of any grade in 20% or more of patients included, blurred vision (47%), keratopathy (41%), keratitis (32%), nausea (29%), peripheral neuropathy (24%), fatigue (23%), and increased AST (21%). Grade 3 or higher TRAEs in 5% or more of patients included blurred vision (20%), keratopathy (18%), neutropenia (14%), and keratitis (11%). 11 of the 12 reports of neutropenia and 12 of the 16 cases of peripheral neuropathy occurred in patients treated at doses of 5.8 mg/kg or higher. Ocular AEs led to treatment discontinuation in four patients (6%), with three of the four patients receiving doses of 5.8 mg/kg or higher. Based on clinical data and favorable PK, a 5.0 mg/kg dose on a Q3W regimen with a 2-on, 1-off dose break schedule was selected as the recommended Phase 2 dose, which will be compared to a 4.0 mg/kg Q3W dose in Part 2 of the trial.

“The early data from the MYTX-011 study, showing compelling anti-tumor activity and durable responses in patients with lung cancer, together with a well-tolerated safety profile, are highly encouraging,” said Rebecca Heist, M.D., MPH, Medical Oncologist, Massachusetts General Hospital, Cancer Center. “These findings suggest that MYTX-011 has the potential to become a promising new treatment option for a broad range of NSCLC patients, and we are eager to continue evaluating its efficacy and safety in the ongoing dose expansion phase of the study.”

About KisMET-01

KisMET-01 (NCT05652868) is a multicenter, first-in-human Phase 1 study of MYTX-011 in patients with previously treated, locally advanced or metastatic NSCLC. The study is comprised of two parts: dose escalation (Part 1) in patients with NSCLC of any histology of cMET expression with cMET analyzed whenever tumor tissue is available, followed by dose expansion (Part 2) in cMET-positive (cMET+) patients selected by immunohistochemistry (Ventana SP44). cMET levels are defined as high (≥50% tumor cells with 3+ staining), intermediate (≥25% and <50% with 3+ staining), low (≥25% with 2+ staining, excluding high and intermediate), and ultra-low (≥75% excluding high, intermediate, and low).

About MYTX-011

MYTX-011 is an investigational cMET-targeting ADC, which leverages Mythic’s innovative FateControl™ technology. FateControl™ ADCs are pH engineered to unbind their target after internalization, intended to improve both tumor uptake and drug exposure for improved safety, tolerability and efficacy. MYTX-011 is currently being evaluated in the Phase 1 KisMET-01 clinical trial, a first-in-human, open-label, multi-center, dose escalation and dose expansion study enrolling patients with locally advanced, recurrent or metastatic NSCLC (NCT05652868).

About Mythic Therapeutics

Mythic Therapeutics is a product-platform company developing a pipeline of antibody-drug conjugates (ADCs) designed to exhibit unparalleled therapeutic index and efficacy. The Company’s FateControl™ technology aims to enhance ADC uptake in targeted tissues by manipulating the fate of the ADC within the cell, thereby expanding the diseases and patient profiles that could be treated with Mythic’s ADCs. The company’s major investors include Venrock, Viking Global Investors, and First Round Capital.

For more information, visit: www.mythictx.com and follow on LinkedIn.

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