For Healthcare Professionals

XTX101 Monotherapy and XTX101 and Atezolizumab Combination Therapy in Patients With Advanced Solid Tumors


About the study

This is a first-in-human, Phase 1/2, multicenter, open-label study designed to evaluate the safety and tolerability of XTX101 as monotherapy and XTX101 and atezolizumab combination therapy in patients with advanced solid tumors.

Who can take part

You may be eligible to participate in the study if you meet the following criteria:


Inclusion Criteria:

Disease Criteria -

Part 1A and 1C: Any histologically or cytologically confirmed solid tumor malignancy that is locally advanced or metastatic and has failed standard therapy, or standard therapy is not curative or available;

Part 1B:

  1. Any histologically or cytologically confirmed solid tumor malignancy for which anti-PD-1 or anti-PD-L1 treatment is approved and has progressed on or after prior anti-PD-1 or anti-PD-L1 therapy.
  2. Patients with metastatic castrate-resistant prostate cancer if they have progressed on at least 2 lines of systemic therapy
  3. Patients with extensive stage small cell lung cancer (SCLC) after at least 1 line of prior therapy
  4. Patients with microsatellite stable colorectal cancer after at least 2 lines of prior therapy
  5. ECOG performance status of 0 or 1
  6. Adequate organ function
  7. Part 1B and Part 1C only: measurable disease per iRECIST


Exclusion Criteria:

  1. Received prior treatment with anti-CTLA-4 therapy
  2. Received prior immune-checkpoint therapy and experienced Grade 3 or greater toxicity lasting greater than 6 weeks
  3. Received prior systemic anticancer therapy within 4 weeks prior to study treatment
  4. Received prior radiotherapy within 2 weeks prior to study treatment
  5. Has a diagnosis of immunodeficiency
  6. Has known malignancy (other than disease under study) that is progressing or has required active treatment within the past 3 years
  7. Has an active autoimmune disease that has required systemic treatment in past 2 years, including the use of disease modifying agents, corticosteroids or immunosuppressive drugs
  8. Has an active infection requiring systemic intravenous therapy within 4 weeks prior to study treatment, or oral therapy within 2 weeks prior to study treatment
  9. Has a history of severe hypersensitivity reaction (≥ Grade 3) to any study intervention and/or any of its excipients
  10. Has a known psychiatric or substance abuse disorder that would interfere with the participant's ability to cooperate with the requirements of the study
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Study Locations

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How to Apply

Contact the study center to learn if this study is a good match for you.

Study’s details


Advanced Solid Tumor

Age (in years)



Phase 1/Phase 2

Participants needed


Est. Completion Date

Mar 30, 2026

Treatment type



Xilio Development, Inc. identifier


Study number


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