Ep195: Ken Song on T-cell Engagers for Autoimmune Diseases

Episode Summary

Executive Summary: Ken Song discusses leaving RazeBio after its $4.1B Bristol Myers Squibb acquisition and founding Candid Therapeutics to pursue biospecific T-cell engager antibodies for autoimmune disease. He explains why he chose this space, how he licensed clinical-stage assets globally, the challenges with FDA development pathways, and why he believes one-cycle T-cell engager therapy could deliver scalable immune reset outcomes across major autoimmune indications.

Main Topics: From RazeBio exit to new venture (Priority: 5/5): Song reflects on leading RazeBio to a successful $4.1B acquisition by Bristol Myers Squibb and how that outcome freed him to explore his next move rather than retire. Why autoimmune disease and T-cell engagers (Priority: 5/5): He explains that early CAR-T autoimmune data suggested an immune reset, but T-cell engager antibodies may offer a more scalable, vial-based version of the same biology. Asset sourcing and licensing strategy (Priority: 5/5): Candid identified clinical-stage BCMA and CD20 T-cell engagers, many from China, and negotiated dual in-licensing before formal company launch. Clinical development and FDA friction (Priority: 5/5): The company pushed for rapid human data, but encountered an FDA/CDER requirement to restart at very low doses, leading Candid to pursue Europe and China for early studies. Target profile and competitive positioning (Priority: 4/5): Song argues Candid’s molecules have strong safety and efficacy differentiation, especially lower cytokine release syndrome than marketed comparators, and could become first-in-class or best-in-class in large autoimmune markets. Operating philosophy and speed (Priority: 4/5): He emphasizes real-time decision-making, minimizing delays, and treating time as more valuable than small cost savings in a fast-moving biotech race. Elevate and East Asian biotech leadership (Priority: 3/5): Song describes Elevate as a network and data-driven effort to understand why East Asians are underrepresented in biotech CEO/C-suite roles and to support future leaders.

Key Arguments: Radiopharmaceuticals were validated by market and clinical data, making RazeBio attractive enough for multiple pharma bidders. Autoimmune disease may be transformable through deep B-cell/plasma-cell depletion, as seen in CAR-T studies showing immune reset. T-cell engagers are a more practical and scalable alternative to CAR-T because they can be delivered as a one-cycle, vial-based therapy. Candid’s focus on clinical-stage, de-risked assets with existing human data improves the odds of rapid value creation. The company’s BCMA and CD20 programs appear safer than many comparators, with lower CRS and manageable outpatient profiles. Timing mattered: Candid entered China-focused licensing before the market became crowded with global bidders. Rapid execution is a strategic advantage; small time savings compound into major capital and development benefits. Multiple autoimmune indications can be pursued, but the company wants only the strongest signals and best differentiated opportunities. Candid believes first-mover advantage in a large class can still capture a disproportionate share of market value, even with several eventual competitors.

Data Points: RazeBio acquisition value: $4.1 billion - Bristol Myers Squibb acquired RazeBio in December 2023. Candid venture funding: $370 million - Capital raised for Candid Therapeutics at launch/Series A. Timing from launch to data: < 16 months - Song says the company moved from hypothesis to clinical proof in less than a year and a half. Clinical-stage assets licensed: 2 - Candid in-licensed one BCMA and one CD20 T-cell engager. BCMA program patient data: 40 patients - Suzutamig oncology dataset used for diligence. CD20 program patient data: 90 patients - CD20 T-cell engager had been dosed in lymphoma patients before licensing. Autoimmune studies opened: >10 diseases - Candid opened studies across more than ten autoimmune diseases early in development. China-based workforce: 15 employees - Candid has roughly a third of the company in China, including a general manager. Total autoimmune diseases considered: 100+ narrowed to 10 - The team reduced a broad universe of autoimmune diseases to a focused set of targets. Autoimmune disease prevalence in U.S.: 20-40 million people - Song cites very large potential market size across autoimmune conditions. CRS with marketed BCMA comparator: 60-70% - He contrasts Tecvayli label data with Candid’s lower observed CRS rates. Candid CRS rates in lead molecules: 20-30% - Observed CRS rates for Suzutamig and CD20 program were described as less than half of Tecvayli's. FDA development constraint: Start at super-low doses / highly refractory patients - CDER reportedly required a far more conservative plan than Candid wanted. Potential class market share: ~70% for first mover - Song argues a differentiated first-in-class product can capture the majority of a class opportunity. Potential number of market players: 3-5 - He expects several T-cell engagers could ultimately reach market in autoimmune disease.

Pivotal Quotes: "What if you could do this type of modality that you can make through more competent means, put it in a vial, inject it once every month or so, and get a similar result?" — Ken Song: Explaining the core hypothesis behind using T-cell engagers instead of CAR-T for autoimmune disease. "We have more experience, I believe, now with T-cell engagers and autoimmune disease than anyone in the world, any company, any institution, we have more experience." — Ken Song: Describing Candid’s early clinical position and accumulated know-how. "The thing that really caught us by surprise is that... one part of it is regulating... a relatively toxic, non-scalable therapy... and on the other hand... not really providing what I would consider a reasonable development path for companies." — Ken Song: Critiquing the FDA/CDER versus CBER split in how autoimmune cell therapy and T-cell engagers are regulated.

Implications: If Candid’s data hold up, T-cell engagers could become a scalable “immune reset” platform for major autoimmune diseases, creating a new drug class with blockbuster potential and reshaping competition, regulation, and treatment expectations.