France-based Ipsen (Euronext: IPN; ADR: IPSEY) has agreed to acquire Switzerland-based Memo Therapeutics AG in a deal totaling more than EUR 700 million, centered on potravitug, a Phase II monoclonal antibody targeting BK polyomavirus infection in kidney transplant recipients. The acquisition extends Ipsen's rare disease portfolio into post-transplant infectious complications, an indication with no approved therapies, and is the firm's second major acquisition announcement a matter of days after announcing the acquisition of Kartos Therapeutics for up to USD 1.75 billion.
Under the terms of the definitive share purchase agreement, Memo Therapeutics shareholders will receive EUR 200 million at closing on a cash-free, debt-free basis, with deferred payments contingent on development, regulatory approval, and sales-based milestones bringing total potential consideration in excess of EUR 700 million. Geographic rights were not disclosed. As a condition precedent to closing, Memo Therapeutics' assets unrelated to potravitug — including its DROPZYLLA antibody discovery platform and its USD 328 million collaboration with CSL on recombinant polyclonal IgG technology — will be carved out into a newly incorporated entity, Memorises Bio, retained by existing shareholders. The transaction is expected to close in Q3 2026, subject to customary conditions, and its financial impact has been factored into Ipsen's current full-year guidance.
Potravitug is a monoclonal antibody directed against the BK virus VP1 capsid protein. It blocks viral attachment and cellular entry, preventing infection of renal tubular epithelial cells and subsequent viral replication. BK polyomavirus (BKPyV), which is latent in the majority of the population, reactivates in approximately 30% of kidney transplant recipients within the first year post-transplant due to the immunosuppression required to prevent graft rejection. Uncontrolled viremia can progress to BK polyomavirus-associated nephropathy (BKPyVAN), a condition that significantly increases the risk of graft loss and the need for re-transplantation. Current clinical management relies on reducing immunosuppression — a strategy that trades viral control for an elevated risk of allograft rejection. No approved targeted antiviral therapy exists for BKPyV in any market.
The Phase II SAFE KIDNEY II trial, the largest placebo-controlled study conducted in this population, enrolled 95 patients across 22 US sites. Complete data presented at the American Transplant Congress 2026 demonstrated that 24.4% of potravitug-treated patients achieved undetectable BKPyV-DNAemia by week 38, compared with 13.0% in the placebo group. Viral load reductions exceeding 2-log₁₀ were observed in 40.3% versus 24.7% of patients, respectively. By week 20, biopsy-proven BKPyVAN had declined from 51.2% to 31.6% in the treatment group, with no change in the placebo arm. Potravitug was well tolerated, with no treatment-related serious adverse events reported. Ipsen has indicated that the totality of SAFE KIDNEY II data supports initiation of the pivotal Phase II/III SAFE KIDNEY III trial later in 2026. The US FDA granted potravitug Fast Track designation in May 2023, and the EU granted orphan drug designation in December 2025.
No approved monoclonal antibody currently targets BKPyV. Japan-based Asahi Kasei's recently completed acquisition of Aicuris Anti-infective Cures AG included AIC468, an antisense oligonucleotide targeting BK virus in Phase I, representing a mechanistically distinct early-stage approach in the same indication. Cidofovir and leflunomide have been used off-label but carry significant toxicity profiles and lack controlled efficacy data in BKPyVAN, leaving potravitug without an approved comparator.