When Jonathan Violin looks at the current crop of Alzheimer's treatments, he sees progress—and a troubling pattern. Leqembi and Kisunla have finally proven that clearing brain plaque can slow cognitive decline, validating decades of research. But both drugs carry boxed warnings for potentially dangerous brain swelling and bleeding, require regular MRI monitoring, and demand hours-long intravenous infusions every few weeks.
"The efficacy is there," Violin said in an interview last week. "But we think we can do better on the safety and convenience side."
That conviction—shared by a syndicate of deep-pocketed backers—is why Korsana Biosciences emerged from stealth mode on February 18 with $175 million already in the bank. The Waltham, Massachusetts startup, which Violin now leads as CEO, is developing KRSA-028, a subcutaneous antibody engineered to slip across the blood-brain barrier and attack Alzheimer's plaque without triggering the complications that have shadowed the field's recent breakthroughs.
The financing came in two tranches: $25 million in seed capital from Fairmount Funds and Venrock Healthcare Capital Partners, followed by a $150 million Series A that closed last September. Wellington Management and TCGX co-led the larger round, joined by J.P. Morgan Life Sciences Private Capital, Janus Henderson Investors, Sanofi Ventures, and Foresite Capital. It's enough runway to push KRSA-028 through proof-of-concept studies by late 2027, perhaps longer if the data warrant patience.
The Science Gambit
What makes Korsana's antibody different starts with how it gets into the brain. Most Alzheimer's drugs struggle to cross the blood-brain barrier in meaningful concentrations, forcing developers to use high systemic doses—which, in turn, can trigger the immune reactions behind those troubling brain imaging abnormalities, known in the field as ARIA.
KRSA-028 takes a different route. The company's proprietary platform, called THETA, hitches the antibody to a molecular shuttle that binds to transferrin receptor 1, a protein naturally abundant on brain capillaries. Once across, the drug targets pyroglutamate-modified amyloid beta—a particularly sticky variant of the protein that accumulates in plaques. Korsana's pitch: higher brain exposure, lower overall dose, fewer side effects.
The approach borrows from a playbook that's gaining momentum. Roche is advancing trontinemab, a bispecific that similarly exploits transferrin receptor transport and showed less than 5% incidence of serious brain swelling in mid-stage trials presented last year. AbbVie, rarely one to overpay, shelled out $1.4 billion up front in December 2024 to acquire Aliada Therapeutics and its own brain-penetrant antibody against pyroglutamate amyloid.
Then there's the delivery question. Korsana is betting on subcutaneous injections—potentially self-administered—as an advantage over the infusion centers required for Leqembi and Kisunla. It's a selling point, though the window may be narrowing. Eisai and Biogen introduced a subcutaneous maintenance formulation of Leqembi in August, eroding some of that differentiation.
The Paragon Pedigree
Korsana is the seventh company to spin out of Paragon Therapeutics, a Cambridge-based incubator with a growing track record of engineering antibodies for difficult targets. Violin himself is no stranger to the venture-backed biotech circuit—he previously founded Viridian Therapeutics (now eyeing commercialization in thyroid eye disease), Dianthus Therapeutics, and Quellis Biosciences. He's since moved into a venture partner role at Fairmount while helming Korsana.
That experience matters when a company commits to timelines as aggressive as this one. First-in-human studies are slated to kick off in early 2027. Initial safety and pharmacokinetic data should follow by mid-year, with the critical proof-of-concept plaque reduction readout expected by year-end. It's a schedule that assumes few regulatory hiccups and tight execution—not always a safe bet in neuroscience.
The Stakes
The Alzheimer's market is as daunting as it is enormous. Nearly 13 million Americans are projected to live with the disease by 2050, according to the Alzheimer's Association, with annual costs in the U.S. alone expected to approach $1 trillion. The approval of Leqembi and Kisunla marked a watershed, but uptake has been slower than hoped, hampered by the burden of monitoring for side effects and the logistics of infusion therapy.
For Korsana, that creates an opening—but only if the science holds. Can THETA truly deliver meaningful drug concentrations to the brain at doses low enough to sidestep ARIA? Will subcutaneous delivery prove practical at scale? And perhaps most crucially, will targeting pyroglutamate amyloid beta clear plaques as effectively as the broader-spectrum antibodies already on the market?
Investors are willing to wager $175 million that the answers tilt favorably. The rest of us will know by the end of next year whether their optimism was warranted—or premature.
