This section highlights FDA-related milestones and regulatory updates for drugs developed by Xilio Therapeutics (XLO).
Over the past two years, Xilio Therapeutics has reported clinical trial outcomes, regulatory submissions, approvals, and other FDA events for drugs and therapies such as
XTX501, vilastobart, XTX301, and XTX101. For definitions of regulatory abbreviations such as NDA, BLA, or PDUFA, see the event status legend.
Select a button below to view the list of FDA events for that drug.
XTX501 FDA Regulatory Events
XTX501 is a drug developed by Xilio Therapeutics for the following indication: in patients with metastatic non-small cell lung cancer before expanding development to other solid tumor types, including tumors that are insensitive to PD-1 therapy.
This drug is under review by the U.S. Food and Drug Administration (FDA).
Below is a timeline of key regulatory milestones for this therapy.
- Drug:
- XTX501
- Announced Date:
- March 23, 2026
- Indication:
- in patients with metastatic non-small cell lung cancer before expanding development to other solid tumor types, including tumors that are insensitive to PD-1 therapy.
Announcement
Xilio Therapeutics, Inc. announced pipeline progress and business updates
AI Summary
Xilio Therapeutics, a clinical-stage biotech focused on masked immuno-oncology therapies, reported progress across its pipeline and business. XTX501, a bispecific PD-1 / masked IL-2 designed to be best-in-class, remains on track for an IND submission in mid-2026 and to start a Phase 1 trial in the second half of 2026.
The company is advancing multiple masked T cell engager programs, including a potential first-in-class multi-specific engager targeting PSMA and STEAP1, plus a program in collaboration with AbbVie. Xilio plans to present new preclinical data at AACR for a masked T cell engager targeting CLDN18.2. Separately, efarindodekin alfa (masked IL-12) is in a Phase 2 trial for advanced solid tumors, with an option data package to Gilead expected in the first half of 2027.
On finances, Xilio said its cash should fund operations through the end of 2027. That outlook excludes possible collaboration milestone payments and up to $36.2 million if certain warrants are exercised.
Read Announcement
Vilastobart FDA Regulatory Timeline and Events
Vilastobart is a drug developed by Xilio Therapeutics for the following indication: In Patients with Microsatellite Stable Colorectal Cancer.
This drug is under review by the U.S. Food and Drug Administration (FDA).
Below is a timeline of key regulatory milestones for this therapy.
- Drug:
- vilastobart
- Announced Date:
- November 7, 2025
- Indication:
- In Patients with Microsatellite Stable Colorectal Cancer
Announcement
Xilio Therapeutics, Inc. announced new data from its ongoing Phase 2 clinical trial evaluating vilastobart, a tumor-activated, Fc-enhanced anti-CTLA-4, in combination with atezolizumab (Tecentriq®) in patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC).
AI Summary
Xilio Therapeutics reported Phase 2 data showing a 40% objective response rate (ORR) for vilastobart—an investigational tumor‑activated anti‑CTLA‑4—combined with atezolizumab in pre‑treated patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC) who had no liver metastases and high plasma tumor mutational burden (TMB ≥10 mutations/Mb). Plasma TMB correlated with response (p=0.05). Among 44 treated patients, 27 had no liver mets; 24 were evaluable for plasma TMB and 62.5% were TMB‑high. All responders were TMB‑high and tumor reductions reached up to 71%.
Safety was generally favorable, with mostly Grade 1–2 treatment‑related adverse events; 5% discontinued for treatment‑related AEs and 7% had colitis. Xilio estimates about 55% of MSS CRC patients are plasma TMB‑high based on Guardant360 data, suggesting a larger target population than tissue assays indicate. The company is seeking development partners and is hosting a webcast and call on November 10, 2025 to review the data.
Read Announcement- Drug:
- vilastobart
- Announced Date:
- October 30, 2025
- Indication:
- In Patients with Microsatellite Stable Colorectal Cancer
Announcement
Xilio Therapeutics, Inc. announced that it will present a late-breaking poster presentation for vilastobart, a tumor-activated, Fc-enhanced anti-CTLA-4, at the Society for Immunotherapy of Cancer (SITC) 40th Annual Meeting, taking place from November 5-9, 2025 in National Harbor, Maryland.
AI Summary
Xilio Therapeutics, a clinical-stage biotech company, announced it will present a late-breaking poster on vilastobart at the Society for Immunotherapy of Cancer (SITC) 40th Annual Meeting, November 5–9, 2025, in National Harbor, Maryland. The presentation will summarize Phase 2 data highlighting the response rate of vilastobart, a tumor-activated, Fc-enhanced anti-CTLA-4 antibody, combined with the PD-L1 inhibitor atezolizumab.
The abstract, titled “Plasma Tumor Mutational Burden (pTMB) Enriched for Response to Vilastobart in Combination with Atezolizumab in Patients with Microsatellite Stable (MSS) Metastatic Colorectal Cancer (mCRC),” is numbered 1315. The poster will be on display Friday, November 7, from 9:00 a.m. to 7:00 p.m. EST in Prince George ABC Exhibit Halls at the Gaylord National Resort and Convention Center.
On November 7, the poster will be accessible on Xilio’s website under “Our Approach—Presentations & Publications.” This data aims to show how vilastobart may improve outcomes in MSS mCRC patients with high plasma tumor mutational burden.
Learn more about Xilio’s tumor-activated immuno-oncology pipeline at www.xiliotx.com.
Read Announcement- Drug:
- vilastobart
- Announced Date:
- May 31, 2025
- Indication:
- In Patients with Microsatellite Stable Colorectal Cancer
Announcement
Xilio Therapeutics, Inc. announced updated data from its ongoing Phase 2 clinical trial evaluating vilastobart, a tumor-activated, Fc-enhanced, high affinity binding anti-CTLA-4, in combination with atezolizumab (Tecentriq®) in patients with metastatic MSS CRC.
AI Summary
Xilio Therapeutics, Inc. announced new data from its ongoing Phase 2 clinical trial evaluating vilastobart—a tumor-activated, Fc-enhanced, high affinity anti-CTLA-4 antibody—in combination with atezolizumab (Tecentriq®) for patients with metastatic microsatellite stable colorectal cancer (MSS CRC). The trial focuses on heavily pre-treated patients, with notable results observed in those without liver metastases, where a preliminary objective response rate of 26% was reported. Responses were deep and durable, lasting up to 37 weeks, and were supported by significant tumor biomarker decreases and symptom improvements.
The combination treatment also demonstrated a distinct safety and tolerability profile, showing a low incidence of colitis and other immune-related adverse events. These encouraging results highlight the potential of vilastobart paired with PD-(L)1 inhibitors, not only for addressing MSS CRC but also for a broader range of tumor types resistant to current immunotherapy options.
Read Announcement- Drug:
- vilastobart
- Announced Date:
- April 23, 2025
- Indication:
- In Patients with Microsatellite Stable Colorectal Cancer
Announcement
Xilio Therapeutics, Inc. announced plans to present updated data from its ongoing Phase 2 clinical trial investigating vilastobart, a tumor-activated, Fc-enhanced anti-CTLA-4, in combination with atezolizumab (Tecentriq®) in patients with metastatic microsatellite stable colorectal cancer (MSS CRC) at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting.
AI Summary
Xilio Therapeutics, Inc. is preparing to share updated data from its ongoing Phase 2 clinical trial at the 2025 American Society of Clinical Oncology Annual Meeting in Chicago. The trial is investigating vilastobart, a tumor-activated, Fc-enhanced anti-CTLA-4 antibody, combined with atezolizumab (Tecentriq®), in patients with metastatic microsatellite stable colorectal cancer (MSS CRC). Vilastobart is designed to specifically target the tumor environment by blocking CTLA-4 and depleting regulatory T cells, potentially enhancing anti-tumor effects while reducing side effects seen with standard treatments. This presentation will provide insights into how combining these two therapies could offer a new treatment option for advanced colorectal cancer, highlighting progress in efforts to develop more focused and effective immuno-oncology therapies.
Read Announcement
XTX301 FDA Regulatory Timeline and Events
XTX301 is a drug developed by Xilio Therapeutics for the following indication: Solid tumors.
This drug is under review by the U.S. Food and Drug Administration (FDA).
Below is a timeline of key regulatory milestones for this therapy.
- Drug:
- XTX301
- Announced Date:
- October 3, 2025
- Indication:
- Solid tumors
Announcement
Xilio Therapeutics, Inc. announced multiple upcoming poster presentations at the Society for Immunotherapy of Cancer (SITC) 40th Annual Meeting, taking place from November 6-9, 2025 at the Gaylord National Convention Center in National Harbor, Maryland.
AI Summary
Xilio Therapeutics, Inc. will present multiple posters at the Society for Immunotherapy of Cancer (SITC) 40th Annual Meeting, held November 6–9, 2025, at the Gaylord National Convention Center in National Harbor, Maryland. As a clinical-stage biotech company, Xilio focuses on tumor-activated immuno-oncology therapies aimed at improving cancer treatment while reducing side effects.
On Friday, November 7, Xilio will showcase two clinical data posters from 9:00 a.m. to 7:00 p.m. EST in Exhibit Halls A & B1: Abstract #541 on using ctDNA as a biomarker for response to vilastobart plus atezolizumab in metastatic colorectal cancer and Abstract #567 on IL-12 pharmacology from the first-in-human study of XTX301 (efarindodekin alfa) in advanced solid tumors. On Saturday, November 8, the company will present Abstract #972 on its masked T cell engager programs from 9:00 a.m. to 8:40 p.m. EST in the same halls.
These presentations reflect Xilio’s commitment to delivering targeted, tumor-activated therapies that maximize anti-tumor activity in the tumor microenvironment.
Read Announcement- Drug:
- XTX301
- Announced Date:
- September 9, 2025
- Indication:
- Solid tumors
Announcement
Xilio Therapeutics, Inc. announced the initiation of patient dosing in Phase 2 of an ongoing Phase 1/2 clinical trial evaluating efarindodekin alfa (XTX301), a tumor-activated IL-12, as a monotherapy in patients with certain advanced solid tumors.
AI Summary
Xilio Therapeutics, Inc. announced the start of patient dosing in the Phase 2 portion of its ongoing Phase 1/2 clinical trial for efarindodekin alfa (XTX301), a tumor-activated IL-12, as a monotherapy in patients with certain advanced solid tumors. Initial Phase 1 data showed two partial responses, sustained interferon gamma signaling without tachyphylaxis, and a mostly Grade 1 or 2 safety profile. These results support the recommended Phase 2 dose and schedule for further study.
Xilio also achieved a $17.5 million development milestone under its Gilead Sciences license agreement, extending its cash runway into the first quarter of 2027. The trial has completed Phase 1A dose escalation, and enrollment in the Phase 1B monotherapy expansion is ongoing. XTX301 aims to reprogram “cold” tumors into inflamed “hot” tumors by activating immune cells directly in the tumor microenvironment, potentially improving outcomes for patients with diverse solid tumors.
Read Announcement- Drug:
- XTX301
- Announced Date:
- December 19, 2024
- Indication:
- Solid tumors
Announcement
Xilio Therapeutics, Inc announced plans to present initial data from its ongoing Phase 2 trial for vilastobart (XTX101), a tumor-activated, Fc-enhanced, high affinity binding anti-CTLA-4, in combination with atezolizumab (Tecentriq®) in patients with metastatic microsatellite stable colorectal cancer (MSS CRC) at the ASCO Gastrointestinal (ASCO GI) Cancers Symposium in San Francisco, California from January 23-25, 2025.
AI Summary
Xilio Therapeutics, Inc. announced that it plans to share initial data from its ongoing Phase 2 trial for vilastobart (XTX101), a tumor-activated, Fc-enhanced, high affinity binding anti-CTLA-4 antibody. The trial is testing the combination of vilastobart with atezolizumab (Tecentriq®) in patients with metastatic microsatellite stable colorectal cancer (MSS CRC). This data will be presented at the ASCO Gastrointestinal (ASCO GI) Cancers Symposium, which will take place in San Francisco, California from January 23-25, 2025.
The presentation is expected to detail the clinical insights and potential benefits of the combination therapy in treating MSS CRC. This move underscores Xilio Therapeutics’ commitment to developing innovative immuno-oncology therapies aimed at improving outcomes for patients with challenging cancer types.
Read Announcement
XTX101 FDA Regulatory Events
XTX101 is a drug developed by Xilio Therapeutics for the following indication: Solid Tumor.
This drug is under review by the U.S. Food and Drug Administration (FDA).
Below is a timeline of key regulatory milestones for this therapy.
- Drug:
- XTX101
- Announced Date:
- January 21, 2025
- Indication:
- Solid Tumor
Announcement
Xilio Therapeutics, Inc announced initial data from its ongoing Phase 2 clinical trial evaluating vilastobart (XTX101), a tumor-activated, Fc-enhanced, high affinity binding anti-CTLA-4, in combination with atezolizumab (Tecentriq®) in patients with metastatic microsatellite stable colorectal cancer (MSS CRC).
AI Summary
Xilio Therapeutics, Inc. announced encouraging initial results from its ongoing Phase 2 trial evaluating vilastobart (XTX101), a tumor-activated, Fc-enhanced anti-CTLA-4 antibody, in combination with atezolizumab (Tecentriq®) for patients with metastatic microsatellite stable colorectal cancer (MSS CRC). In patients without liver metastases, the trial showed a 27% preliminary response rate, with several partial responses that were accompanied by significant decreases in carcinoembryonic antigen (CEA) and circulating tumor DNA (ctDNA) levels and improvements in clinical symptoms. The data also highlighted a differentiated safety and tolerability profile, with a low incidence of immune-related adverse events. These results suggest that adding vilastobart may enhance the efficacy of PD-(L)1 inhibitors in a patient population that has historically shown resistance to immunotherapy. Xilio plans to present further data and follow-up results later this year.
Read Announcement
