NCT06043817 · Antares Therapeutics, Inc
First-In-Human Study of STX-721 in Participants With Locally Advanced or Metastatic Non-Small Cell Lung Cancer Harboring EGFR Exon 20 Insertion Mutations
What this study is about
Study STX-721-101 is an open label, Phase 1/2 study evaluating the safety, tolerability, how the drug moves through the body (PK) exposure, and preliminary antitumor activity of STX-721 in participants with non-small cell lung cancer (NSCLC) carrying EGFR/HER2 exon 20 insertion (ex20ins) mutations.
View original scientific description
Study STX-721-101 is an open label, Phase 1/2 study evaluating the safety, tolerability, pharmacokinetic (PK) exposure, and preliminary antitumor activity of STX-721 in participants with non-small cell lung cancer (NSCLC) carrying EGFR/HER2 exon 20 insertion (ex20ins) mutations.
Interventions
DRUG
STX-721/PFL-721 (Escalated)
STX-721/PFL-721 dose will be escalated per cBLRM-design.
DRUG
STX-721/PFL-721 (3 dose levels)
Participants will receive STX-721/PFL-721 at one of three dose levels.
DRUG
STX-721/PFL-721 (RP2D)
Participants will receive the RP2D of STX-721/PFL-721.
Primary outcome measures
Part 1 Dose Escalation (MTD): Dose Escalation - Number of participants who experience at least 1 DLT during the first 28 days of treatment
Time frame: 28 days
Part 1 Dose Escalation (OBD): Dose Escalation - Number of participants who experience at least 1 DLT during the first 28 days of treatment
Time frame: 28 days
Part 2 RP2D Selection: C(max) of STX-721/PFL-721
Time frame: 1 year
Part 2 RP2D Selection: AUC(0-inf) of STX-721/PFL-721
Time frame: 1 year
Part 2 RP2D Selection: AUC(0-t) of STX-721/PFL-721
Time frame: 1 year
Part 2 RP2D Selection: AUC(0-τ) of STX-721/PFL-721
Time frame: 1 year
Part 2 RP2D Selection: Number of participants with confirmed objective response rate (ORR) defined as the percentage of participants with partial response (PR) or complete response (CR) based on RECIST v1.1 per investigator assessment.
Time frame: 1 year
Part 3 Dose Expansion: Number of participants with confirmed ORR defined as the percentage of participants with PR or CR based on RECIST v1.1 per investigator assessment.
Time frame: 1 year
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- 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 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 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 th
Where
- Duarte, California
- Huntington Beach, California
- Irvine, California
- Charlotte, North Carolina
- Philadelphia, Pennsylvania
- Nashville, Tennessee
- Houston, Texas
- Salt Lake City, Utah
- Fairfax, Virginia
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced May 22, 2026 · Source of record for eligibility and locations