Ep210: Cameron Turtle on Long-Lasting Antibodies for Immune Disorders

Cameron Turtle's journey into biotech began with childhood in Pullman, Washington, where he grew up in a unique environment blending academic and agricultural influences. His father was a finance professor at Washington State University, and Turtle developed a strong foundation in STEM subjects while balancing athletics, particularly football and track, with intellectual pursuits like math competitions. This formative environment instilled a work ethic he credits to farm labor and team sports that prepared him for biotech's challenges.

Turtle pursued bioengineering at the University of Washington, drawn by the program's breadth and the intersection of engineering and medicine. A Washington Scholars Program full-ride scholarship kept him in-state and eventually led to his meeting his wife there. His undergraduate research focused on muscle mechanics, which evolved into clinical applications studying inherited cardiomyopathies during a Rhodes Scholarship DPhil at Oxford. Witnessing Myocardia's formation around 2012-2013 crystallized his decision to pursue biotech rather than academic science, as he recognized the opportunity to actually treat patients rather than merely understand disease mechanisms.

After Oxford, Turtle spent time in management consulting at McKinsey, viewing it as an MBA in biotech business fundamentals. He worked across medical devices, biotech, pharma, and payer business models, gaining insight into R&D productivity patterns and identifying genetically-defined diseases as showing 3x higher probability of success. Through this network, he was introduced to Neil Kumar, who had launched Myocardia at Third Rock and was starting Bridge Therapeutics. Joining Bridge as an early employee, Turtle experienced scaling from single digits to over 500 employees and witnessed the validation of the portfolio approach to rare genetic diseases, particularly the amyloid cardiomyopathy space.

After five years at Bridge, Turtle sought to return to early-stage development and discovery work, as his enthusiasm waned with larger organizational complexity. He was introduced to Fairmount Funds, a hedge fund that transitioned from investing in public biotech to creating companies. Fairmount recognized that validated therapeutic targets, particularly monoclonal antibodies, hadn't been broadly optimized using half-life extending modifications (YTE technology) developed 20 years prior but with expired patents.

Spire was spun out from Fairmount's Paragon Therapeutics in 2023 with focus on three IBD targets: alpha-4 beta-7 (same as Takeda's $6.5-7 billion annual drug but potentially underdosed), TL1A (promising but not yet approved), and the p19 subunit of IL-23. The YTE modification increases neonatal Fc receptor (FcRn) binding at low pH, causing antibodies to be recycled rather than degraded, extending half-life approximately threefold without impacting safety, efficacy, or immunogenicity.

The breakthrough opportunity came when J&J published the VEGA trial showing dual-target combinations achieved 47% clinical remission versus ~25% for individual agents in ulcerative colitis. This demonstrated that combining mechanistically distinct antibodies could overcome the therapeutic ceiling in IBD. Turtle and team designed an ambitious platform study called Skyline testing six active agents in a single trial, enabling efficient comparison of monotherapies against placebo and multiple combinations against their components, roughly halving the patient population and study arms required compared to separate trials.

Spire has raised $1.6 billion with over $1.1 billion remaining on balance sheet. Rather than pursuing incremental convenience improvements, Turtle emphasizes the company is developing first-in-class combinations in IBD and hidradenitis suppurativa, testing TL1A opportunities in rheumatic diseases, and running innovative efficient trial designs. The company targets diseases affecting over 5 million people in the US, seeking meaningful efficacy gains rather than marginal improvements.

Turtle positions Spire's competitive advantage on several fronts: the three combinations being tested are highly differentiated versus competitors' combinations (which often mix existing pipeline assets, oral/injectable combinations, or different dosing frequencies); the long-acting co-formulated approach provides elegant product profiles; and the company maintained sufficient capital to advance multiple programs without running into gambler's ruin, a real risk in biotech. The thesis resonated with public market investors given Fairmount's track record building several multi-billion dollar companies using similar approaches.