Xilio Therapeutics Secures $35.8M Funding, Advances Masked Immuno-Oncology Pipeline with Key Development Milestones
Key Insights
Xilio Therapeutics received $35.8 million in gross proceeds from Series B warrant exercises by major investors including Gilead Sciences, extending cash runway into Q2 2027.
The company achieved a development milestone for its masked antibody program under the AbbVie (search) collaboration and nominated a development candidate for its CLDN18.2 (search)-targeting T cell engager program.
Xilio plans to submit an IND application for XTX501 in mid-2026 and advance multiple masked T cell engager programs into clinical development by 2027.
Xilio Therapeutics announced significant corporate developments and funding achievements that strengthen its position in advancing masked immuno-oncology therapies. The clinical-stage biotechnology company received $35.8 million in gross proceeds from Series B warrant exercises, including full participation from strategic investors Coastlands Capital (search), Frazier Life Sciences (search), and Gilead Sciences.
The funding extends Xilio's anticipated cash runway into the second quarter of 2027, providing crucial resources to advance its differentiated pipeline of masked I-O therapies designed to improve cancer treatment outcomes while reducing systemic side effects.
Development Program Advances
Xilio achieved a development milestone for its masked antibody-based immunotherapy program under its collaboration agreement with AbbVie (search). The company also nominated a development candidate for its wholly-owned masked T cell engager program targeting CLDN18.2 (search), a tumor-associated antigen with broad therapeutic potential across gastric, pancreatic, esophageal, and lung cancers.
"2025 was marked by robust execution at Xilio as we delivered on key priorities across our deep portfolio of differentiated I-O therapies, demonstrated additional clinical validation of our masking technology and further strengthened our financial position through strategic partnerships and our recent equity financing," said René Russo, Pharm.D., president and chief executive officer of Xilio.
Clinical Development Timeline
The company outlined ambitious development milestones for 2026 and 2027. Xilio plans to submit an investigational new drug (IND) application for XTX501 in mid-2026, with initial Phase 1 data expected in the second half of 2027, subject to FDA clearance.
Additional planned milestones include nominating a development candidate for the STEAP1 (search) program, a masked T cell engager with co-stimulation, in the first half of 2026. The company aims to advance at least two masked T cell engager programs into IND-enabling studies and submit IND applications for those programs in 2027.
For its partnership programs, Xilio expects to deliver the Phase 1/2 option data package to Gilead for the efarindodekin alfa (search) program in the first half of 2027.
Leadership Changes
Sara Bonstein was appointed as chair of the board of directors, succeeding Paul Clancy who retired after five years of leadership. Bonstein brings more than 10 years of experience as a chief financial officer for public biotechnology companies and currently serves as CFO of Insmed, Inc. She has been a board member since August 2021.
"Sara has been an invaluable member of our board since 2021 and brings more than two decades of executive leadership in finance, corporate strategy and business operations in the biotechnology industry, as well as extensive experience advancing novel therapies from discovery through commercialization," Dr. Russo stated.
Financial Position
As of December 31, 2025, Xilio estimates cash and cash equivalents of $137.5 million, including the $35.8 million received from warrant exercises in the fourth quarter of 2025. Based on current operating plans, the company anticipates this funding will support operations and capital expenditure requirements into the second quarter of 2027.
The Series B warrants were originally issued in connection with a follow-on public offering completed in June 2025, demonstrating continued investor confidence in Xilio's proprietary masking technology platform.
Technology Platform
Xilio's proprietary masking technology is designed to optimize the therapeutic index by localizing anti-tumor activity within the tumor microenvironment. The company's pipeline includes novel masked I-O molecules aimed at significantly improving outcomes for cancer patients while minimizing the systemic side effects associated with current immunotherapy treatments.
The company maintains strategic partnerships with major pharmaceutical companies including AbbVie (search), Gilead, and Roche, validating the potential of its masking technology platform across multiple therapeutic applications.