Vir Biotechnology (NASDAQ:VIR) used its latest investor call to outline a new strategic collaboration with Astellas to advance VIR-5500, a PSMA-directed, dual-masked T-cell engager for prostate cancer, and to review positive phase I data in metastatic castration-resistant prostate cancer (mCRPC) alongside its 2025 financial results.
Strategic collaboration with Astellas
Chief Executive Officer Marianne De Backer described the agreement as a “landmark” partnership designed to accelerate global development and commercialization of VIR-5500 across earlier and later lines of prostate cancer. De Backer said Vir believes VIR-5500 has the potential to be a best-in-class T-cell engager, and added that the phase I data shared on the call increase confidence in the program’s emerging safety and efficacy profile.
How VIR-5500 and PRO-XTEN are intended to address solid tumor toxicity
De Backer highlighted the company’s PRO-XTEN platform, which uses a “universal dual-masking” design intended to shield both the tumor-antigen and CD3 binding sites until proteases in the tumor microenvironment cleave linkers and unmask the active molecule. Vir argues this approach can reduce systemic T-cell activation and cytokine release syndrome (CRS), potentially enabling higher dosing, a wider therapeutic window, and less frequent administration supported by the XTEN masks’ half-life extension.
Vir framed the unmet need in mCRPC as substantial, noting that five-year survival for mCRPC patients is about 30% and estimating roughly 100,000 mCRPC patients in the U.S. and Europe.
Phase I update: efficacy signals at higher Q3W doses
Chief Medical Officer Mark Eisner reviewed phase I monotherapy data for VIR-5500, which will be presented at ASCO GU (oral presentation) and were current as of a January 9, 2026 cutoff. Vir enrolled 58 patients with advanced mCRPC across weekly and every-three-week (Q3W) regimens, and Eisner said all escalation cohorts cleared the dose-limiting toxicity (DLT) period.
Patients were heavily pretreated, with a median of four prior lines of therapy (up to seven). Eisner said 95% had prior taxane chemotherapy; 93% had bone metastases; 45% had visceral involvement; and 18% had liver metastases. About half were RECIST-evaluable at baseline.
Vir’s development focus is now centered on Q3W doses at or above 3,000 micrograms/kg, which Eisner said is where the company is seeing the clearest clinical signals. In that dose range, Vir reported deep PSA declines and objective responses among RECIST-evaluable patients. Specifically, in 11 RECIST-evaluable patients at Q3W doses ≥3,000 micrograms/kg, five experienced objective responses (four confirmed and one pending confirmation). Vir also reported that at these higher doses, 82% of patients achieved PSA50, more than half achieved PSA90, and nearly one-third achieved PSA99.
Eisner also discussed an exploratory analysis using PSMA PET total tumor volume assessed by RESIP criteria, stating that reductions in PSMA-avid tumor volume at higher doses correlated with PSA declines and RECIST responses.
Safety and tolerability: limited CRS and no observed DLTs
On safety, Eisner said there were no observed DLTs. He reported grade 3 or higher treatment-related adverse events in 12% of patients, mostly laboratory abnormalities, and two discontinuations due to adverse events—one due to spinal cord compression attributed to underlying disease and one due to treatment-related blurred vision.
CRS events were described as limited and predominantly low grade. Eisner said there were no grade 3 CRS events at dose levels of 3,000 micrograms/kg and above. In Q&A, he clarified that one grade 3 CRS event occurred in an earlier, low-dose cohort during intra-participant dose escalation; the patient recovered rapidly.
Vir noted that prophylactic steroids or IL-6 blockade generally were not required, though steroids were evaluated in cycle one in the 4,000 micrograms/kg cohort. Eisner said two events of treatment-related blurred vision were observed with unclear pathophysiology and nonspecific MRI findings that improved toward baseline visual acuity.
Development plans and financial update
Vir said it has selected a preliminary go-forward dose for late-line mCRPC expansion cohorts but did not disclose the exact dose, citing coordination with its new partner. Eisner told analysts the maintenance dose will be in the 3,000 to 3,500 micrograms/kg range. The company expects to initiate dose expansion cohorts in the second quarter of 2026, spanning:
- Late-line mCRPC monotherapy
- First-line mCRPC in combination (including enzalutamide)
- Metastatic hormone-sensitive prostate cancer in combination
Vir also said it will continue dose optimization work to align with the FDA Oncology Center of Excellence’s Project Optimus and aims to support advancement into phase III development in 2027.
Chief Financial Officer Jason O’Byrne detailed collaboration economics, including a 50/50 U.S. profit share with an option for Vir to co-promote and ex-U.S. rights held by Astellas with sales milestones and tiered double-digit royalties for Vir. Global development costs will be split 40% (Vir) and 60% (Astellas), with different rules for U.S.-specific and ex-U.S.-specific studies.
O’Byrne said Vir will receive $335 million in combined upfront and near-term payments (excluding certain payments to Sanofi), including a $315 million upfront composed of $240 million in cash and a $75 million equity investment priced at $10.36 per share (a 50% premium to Vir’s 30-day VWAP as of Feb. 17, 2026). Vir also expects a $20 million manufacturing tech transfer milestone by mid-2027 and is eligible for up to an additional $1.37 billion in development, regulatory, and ex-U.S. commercial milestones, for $1.7 billion total potential combined upfront and milestones (excluding certain third-party payments). Closing remains subject to expiration or termination of the applicable Hart-Scott-Rodino waiting period.
For 2025 results, Vir reported R&D expense of $456 million (down from $507 million in 2024), SG&A expense of $92 million (down from $119 million), and a 2025 net loss of $438 million (versus $522 million in 2024). The company started 2026 with about $782 million in cash, cash equivalents, and investments, excluding the Astellas upfront cash and equity. Including the net effects of the Norgine and Astellas agreements, O’Byrne said Vir expects its cash runway to extend into the second quarter of 2028.
About Vir Biotechnology (NASDAQ:VIR)
Vir Biotechnology, Inc is a clinical‐stage immunology company dedicated to developing therapies that prevent and treat serious infectious diseases. The company leverages a suite of proprietary technology platforms—ranging from antibody isolation and screening tools to cell‐based assays and bioinformatics—to identify and advance antiviral and antibacterial candidates. Its scientific approach centers on harnessing the human immune system through monoclonal antibodies and immunomodulatory agents.
The company’s pipeline includes product candidates targeting influenza A, COVID‐19, HIV, hepatitis B, and tuberculosis.
