aibioBy aibio.space
Sutro has about 14 months of cash at average burn, so we expect a raise
Sutro had $164.3 million at June 30, 2026, and burned $36.3 million a quarter on average. Management says that lasts at least 12 months. We think another raise comes before the cash runs out.
STRO Negative view Cash covers 4.5 quarters at the average burn and less at the recent rate, so we think new money comes within about 14 months.
Sutro Biopharma is a clinical stage oncology company that develops antibody drug conjugates, or ADCs. We think the main story is money. At June 30, 2026 the company held $164.3 million in cash, cash equivalents and short-term investments. Its operating cash burn averaged $36.3 million a quarter over the last four quarters. Management says that cash lasts at least 12 months. Our arithmetic says about 14 months on the average burn, and less on the recent one. We expect Sutro to need new money before the cash runs out.
What the company does and where it is
Its highest priority asset is STRO-004, an ADC directed against tissue factor for solid tumors. The 10-K says the company filed an IND in October 2025, started a Phase 1 trial in November 2025, and began dosing in the dose level 3 cohort in February 2026. The 10-Q now reports early Phase 1 data as of a July 24, 2026 cutoff. The company reports confirmed and unconfirmed partial responses in pancreatic, head and neck and lung cancer at the 3 and 4 mg/kg doses. The text we reviewed gives no patient count and no response rate, and some responses are unconfirmed. Dose limiting toxicities appeared at 5 mg/kg and the maximum tolerated dose is not defined. Treatment-related events in more than 15% of patients were nausea (33%), fatigue (29%) and anemia (18%). Grade 3 anemia was 14%, 6% of patients stopped for adverse events, and the tissue factor target brought nosebleeds (12%), mouth inflammation and eye problems. The next update is due in the first half of 2027. We read this as an early dose-finding study with a safety signal to watch, not as proof of benefit.
STRO-006 is in IND-enabling work. STRO-227, a dual-payload ADC, is in chemistry and manufacturing work, with an IND expected in late 2026 or early 2027. The company also has a collaboration with Astellas, and clinical trials for the first iADC licensed under that deal started in the first quarter of 2026.
Cash and burn
The runway arithmetic is simple. $164.3 million divided by $36.3 million a quarter is 4.5 quarters, or about 14 months. Use the average of the last two quarters instead, $40.3 million a quarter, and the cash lasts less time. We think the recent rate is the better guide, because burn has climbed since its late 2025 low.
Cash fell from $249.0 million at the end of March 2025 to $141.4 million at the end of 2025. It then rose to $202.6 million at March 31, 2026, after a stock sale in February. The 10-Q says the sale raised approximately $110.0 million gross, before underwriting discounts and expenses.
Quarterly operating cash burn was $67.9 million in the first quarter of 2025. It fell to $26.4 million in the quarter ended December 31, 2025. It then rose to $42.3 million in the quarter ended March 31, 2026, and was $38.3 million in the quarter ended June 30, 2026.
What management says about its cash
The 10-Q says the company believes its available cash, cash equivalents and marketable securities “will be sufficient to fund our operations through at least the next 12 months.” We read that as a floor. The same filing says the estimate rests on assumptions that may prove wrong, and that the company “could utilize our available capital resources sooner than we currently expect.” It also says it will need more financing for clinical development.
Management's 12 months is shorter than our 14. The filing counts its 12 months from the filing date, not from June 30, so we think the gap is smaller than it looks. The filing does not say what spending it assumes, so we cannot test the gap. The February sale is already in the June 30 balance, so it does not explain the difference either. Leerink Partners and TD Securities were the representatives of the underwriters on that sale.
Where the money goes
Research and development expense was $39.9 million in the quarter ended September 30, 2025, and $31.7 million in the quarter ended June 30, 2026. The 10-Q describes a March 2025 restructuring plan and a September 2025 reduction of about one third of the remaining employees. The 10-K says the company stopped operations at its San Carlos manufacturing facility, now relies on outside manufacturers, and ended development of luveltamab tazevibulin. Net loss was $38.5 million in each of the last two quarters.
The bull case
The bull case has three parts. Burn is well below its early 2025 level, and R&D of $31.7 million in the June 2026 quarter is the lowest on our chart. Astellas is also paying. The company earned a $10.0 million contingent payment in the first quarter of 2026, tied to Astellas dosing the first subject in a Phase 1 trial in the territory for the first program under the collaboration.
STRO-004 is in the clinic, and the 10-Q reports early partial responses. We think good data would let the company raise money from a stronger position, but the data so far give no response rate.
The bear case
The bear case is about timing and dilution. On the average burn, cash lasts about 14 months. On the recent burn it lasts less. The share count went from 8,584,309 at December 31, 2025 to 16,576,205 at June 30, 2026, and the February sale priced at $13.98 a share. The accumulated deficit is $1,055.0 million, and the company reports a stockholders' deficit of $103.3 million at June 30, 2026.
In June 2025 the company received a Nasdaq notice for a bid price below $1.00. It had until December 17, 2025 to regain compliance. The 10-Q says a 1-for-10 reverse stock split took effect on December 3, 2025, which is why the per-share figures here are small. The 10-Q warns that failure to meet the listing requirements would make its common stock subject to delisting.
Part of the funding came from selling future royalties to Blackstone in June 2023. That obligation still sits on the balance sheet as a deferred royalty obligation. The lead asset is in Phase 1, the class is crowded (the 10-K lists approved ADCs including Enhertu, Trodelvy, Datroway and Tivdak), and we think the outlook depends on data far firmer than the partial responses reported so far.
Our view
We think the bear case is stronger, and the reason is timing. Cash covers about 14 months at the average burn and less at the recent rate. We think a raise made without good data would likely come on weaker terms than one made with it. Either way, we think Sutro is likely to need new money within about 14 months. The STRO-004 data are early and small, and the next update is due in the first half of 2027. On our arithmetic that update would land with about two months of cash left at the average burn.
What to watch, and what would change our mind
The next STRO-004 update, due in the first half of 2027, and the start of expansion cohorts. Quarterly operating cash burn matters most. A run rate at or above the $40.3 million average of the last two quarters shortens the runway. Watch sales under the at-the-market facility with TD Securities, signed on March 23, 2026 after the Jefferies facility ended in March, per the 10-Q. The reverse split addressed the bid price rule; the text we reviewed does not show a Nasdaq closing letter.
What would change our mind: a filing that shows cash covering the company's plans well beyond 14 months, or a partner that pays for the STRO-004 program.