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Testing STX-721 for advanced lung cancer with specific mutations

First-In-Human Study of STX-721/PFL-721 in Participants With Locally Advanced or Metastatic Non-Small Cell Lung Cancer Harboring EGFR or HER2 Exon 20 Insertion Mutations

PHASE1; PHASE2 · Pierre Fabre Medicament · NCT06043817

This study is testing a new treatment called STX-721 to see if it can help people with advanced lung cancer that has specific mutations feel better and respond to the therapy.

Quick facts

PhasePHASE1; PHASE2
Study typeInterventional
Enrollment251 (estimated)
Ages18 Years and up
SexAll
SponsorPierre Fabre Medicament (industry)
Drugs / interventionschemotherapy
Locations24 sites (Duarte, California and 23 other locations)
Trial IDNCT06043817 on ClinicalTrials.gov

What this trial studies

This study evaluates the safety and effectiveness of STX-721 in patients with locally advanced or metastatic non-small cell lung cancer (NSCLC) that have EGFR or HER2 exon 20 insertion mutations. It is an open-label, Phase 1/2 trial that will assess pharmacokinetics and preliminary antitumor activity of the treatment across different dose levels. Participants must have confirmed mutations and measurable tumor lesions, and they will be monitored for treatment response and side effects.

Who should consider this trial

Good fit: Ideal candidates are adults with advanced NSCLC harboring EGFR or HER2 exon 20 insertion mutations who have progressed after prior treatments.

Not a fit: Patients with early-stage lung cancer or those without the specific EGFR or HER2 exon 20 insertion mutations may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could provide a new therapeutic option for patients with a specific type of lung cancer that currently has limited treatment options.

How similar studies have performed: Other studies targeting specific mutations in lung cancer have shown promise, indicating potential for success with this approach.

Eligibility criteria

Show full inclusion / exclusion criteria 
Key Inclusion Criteria:

1. Has histologically- or cytologically confirmed diagnosis of NSCLC Stage IIIB/C or IV not eligible for curative intent surgery or chemoradiation
2. Part 1: Tumor tissue EGFR or HER2 exon 20 insertion mutations confirmed by qualified local laboratories. Parts 2 and 3: EGFR/HER2 exon 20 insertion mutations confirmed by qualified local laboratories
3. Part 1: Has received all approved therapies for advanced or metastatic NSCLC or is ineligible. Part 2 and Part 3: Has received at least 1, but not more than 2, prior lines of approved treatment for advanced or metastatic NSCLC, 1 of which must be platinum-based chemotherapy unless contraindicated
4. Has documented tumor progression (based on radiological imaging)
5. Has new or recent tumor biopsy (collected at screening, if feasible) or archival tumor specimen collected in the past 10 years available for genomic profiling
6. Has at least one measurable tumor lesion per RECIST v1.1
7. Is ≥18 years of age at the time of signing the ICF
8. Has Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1

Key Exclusion Criteria:

1. Has a tumor that is known to harbor EGFR ex20ins p.H773\_V774insH variant, or any EGFR kinase domain activating mutation concurrent with either a T790M and/or C797S resistance mutations
2. Has history (within ≤2 years before screening) of solid tumor or hematological malignancy that is histologically distinct from NSCLC
3. Has symptomatic brain or spinal metastases
4. Has toxicities from previous anticancer therapies that have not resolved to baseline levels or to CTCAE Grade ≤1, except for alopecia and peripheral neuropathy
5. Has any condition for which, in the opinion of the investigator, participation would not be in the best interest of the participant (e.g., could compromise the participant's well-being) or would prevent, limit, or confound the protocol-specified assessments

Where this trial is running

Duarte, California and 23 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.

View on ClinicalTrials.gov →

Conditions: Non-Small Cell Lung Cancer, NSCLC, EGFR/HER2 Exon 20 Insertion Mutation, Exon 20, EGFR, HER2, NSCLC, TKI

Last reviewed 2026-05-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.