OncoMatch/Clinical Trials/NCT05768139
First-in-Human Study of STX-478 as Monotherapy and in Combination With Other Antineoplastic Agents in Participants With Advanced Solid Tumors
Is NCT05768139 recruiting? Yes, currently enrolling (May 2026). This Phase 1/2 trial studies multiple treatments for breast cancer.
Treatment: STX-478 · Fulvestrant · Ribociclib · Palbociclib · Letrozole · Anastrozole · Exemestane — Study STX-478-101 (LY4064809) is a multipart, open-label, phase 1/2 study evaluating the safety, tolerability, pharmacokinetics (PK), and preliminary antitumor activity of STX-478 (LY4064809) in participants with advanced solid tumors with P13Ka mutations. Part 1 will evaluate STX-478 as monotherapy in participants with advanced solid tumors. Part 2 will evaluate STX-478 therapy as combination therapy with fulvestrant in participants with hormone receptor positive (HR+) breast cancer. Part 3 will evaluate STX-478 as combination therapy with endocrine therapy (aromatase inhibitors, fulvestrant or imlunestrant) and a CDK4/6 Inhibitor (either Ribociclib, Palbociclib or Abemaciclib) in participants with HR+ breast cancer. Each study part will include a 28-day screening period, followed by treatment with STX-478 monotherapy or combination therapy.
Check if I qualifyExtracted eligibility criteria
Cancer type
Breast Carcinoma
Tumor Agnostic
Biomarker criteria
Required: PIK3CA mutation
Disease stage
Metastatic disease required
Performance status
ECOG 0–1(Restricted strenuous activity)
Prior therapy
Cannot have received: PI3K/AKT/mTOR inhibitor
Exception: except in certain circumstances
Has had prior treatment with PI3K/AKT/mTOR inhibitor(s), except in certain circumstances
Cannot have received: local or systemic antineoplastic therapy or investigational anticancer agent
Exception: endocrine therapy does not require a washout period if the patient is enrolling in a cohort with the same combination endocrine therapy
Has had treatment with any local or systemic antineoplastic therapy or investigational anticancer agent within 14 days or 4 half-lives, whichever is longer, prior to the initiation of study treatment up to a maximum washout period of 28 days. Endocrine therapy does not require a washout period if the patient is enrolling in a cohort with the same combination endocrine therapy.
Cannot have received: radiotherapy
Has had radiotherapy within 14 days before the initiation of study treatment
Lab requirements
Blood counts
Kidney function
Liver function
Has adequate organ function as defined per protocol
Structured fields extracted by AI. May contain errors — verify against the official protocol.
US trial sites
- Ellison Clinic at Saint John's · Los Angeles, California
- UCSF Medical Center at Mission Bay · San Francisco, California
- University of Colorado Cancer Center · Aurora, Colorado
- Yale-New Haven Hospital · New Haven, Connecticut
- Florida Cancer Specialists ORLANDO/DDU · Lake Mary, Florida
Showing up to 5 US sites. See all sites on ClinicalTrials.gov →
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