Xilio Therapeutics, Inc. (XLO) stock intrinsic value fair value estimate & owner earnings analysis

Xilio Therapeutics, based in Waltham, Massachusetts, is a clinical-stage biotechnology company developing "masked" immuno-oncology drugs designed to become active only inside tumors. It has no product sales. All of its revenue is collaboration and license revenue from two partners: Gilead Sciences, which licensed the IL-12 program (efarindodekin alfa) in March 2024, and AbbVie, which signed a collaboration, license and option agreement in February 2025. Efarindodekin alfa is in a Phase 2 monotherapy trial, with an option data package due to Gilead in the first half of 2027. XTX501 has FDA clearance for a Phase 1/2 trial, and two masked T-cell engager programs are preclinical, with IND filings planned for the second half of 2027. What the business earns. We measure the cash an owner could take out: operating cash flow with working-capital timing swings removed, stock-based pay charged as a real cost, and all capital spending deducted. We treated all capital spending as upkeep because partner revenue does not depend on building capacity. On that basis the company has lost money every year: about $75 million in 2021, $88 million in 2022, $75 million in 2023, $57 million in 2024 and $38 million in 2025. The smaller losses in 2024 and 2025 come mostly from booking partner upfront payments as revenue ($43.8 million in 2025). That cash arrived in advance and is already in the cash balance, so we do not count it a second time. Non-cash gains and costs on the company's stock warrants were excluded. We use the 2021-2025 median, a loss of roughly $74 million a year, as the normal rate of spending. The first half of 2026 was in line, with an operating cash outflow of $41.1 million. Balance sheet. At June 30, 2026 the company had $136.0 million of cash and no borrowings; its last loan was repaid in 2023. Prefunded warrants can be exercised for a nominal price and are effectively shares. Counting them, there are about 19.4 million shares, so cash was about $7.01 per share. The company says this cash will fund its plans into the first quarter of 2028. In other words, the plan is to spend essentially all of it on research. The 1-for-14 reverse split on March 13, 2026 was carried out to address Nasdaq's $1 minimum bid rule. All per-share figures here reflect it. Why the values are low. No program has reached the market, and every future cash inflow depends on something that has not happened yet. Those inflows are: up to $31.0 million of near-term AbbVie milestones and option-extension fees through the first half of 2027 (AbbVie paid a $6.0 million milestone in the first quarter of 2026); a $75.0 million transition fee if Gilead opts into the IL-12 program; and up to $500 million of later Gilead milestones plus royalties from high single digits to mid-teens after an opt-in. Shareholders benefit only from cash that is not spent. The company's stated plan puts its cash into programs whose earning power cannot yet be shown, so today's shareholder is left with only what remains after that plan runs. Base case: spending continues at about $74 million a year, no contingent partner payments arrive, and the cash runs out in the first half of 2028. In today's money the operation is worth about minus $129 million. Against $136.0 million of cash and no debt, about $7 million is left, or $0.36 per share. Bear case: spending runs at the first-half-2026 cash cost of about $89 million a year (operating expenses less stock-based pay and depreciation) as XTX501 and the T-cell engager programs advance, and no partner money arrives. Cash runs out in early 2028, leaving about $4 million of remaining lease obligations on the Waltham facility, whose lease runs to March 2030. The operation is worth about minus $134 million against $136.0 million of cash and no debt, leaving about $2 million, or $0.10 per share. Bull case: AbbVie pays the full $31.0 million of near-term fees, and Gilead opts in and pays the $75.0 million transition fee after the 2027 data package. These are payments on terms already written into signed contracts. The money is spent under the same plan, so spending at about $74 million a year simply runs until about late 2029. The present value of that spending, about $220 million, is set against $136.0 million of cash and about $99 million in present value of partner payments. That leaves about $15 million, or $0.77 per share. Later Gilead milestones and royalties depend on clinical and regulatory success that has not happened, so they are not counted. Not included: 3,443,388 Series C warrants exercisable at $10.50 between June 1 and December 2, 2026 could bring in up to $36.2 million. That money would also add shares and, under the company's plans, would fund more research. What would make this wrong. Clinical results that make a partner opt-in and later milestones likely would change the picture. So would a decision to stop spending and return cash to shareholders. At most, the shares are backed by the cash, about $7 per share at June 30, 2026 and declining as it is spent. A value much above these figures depends on pipeline success that has not yet happened.