The Belgian pharma is buying a two-year-old San Diego biotech for $2bn upfront, the second TCE bet it has placed in months. The thesis: B-cell killers built for cancer can rewire how autoimmune diseases are treated. Candid Therapeutics is two years old. It does not have an approved drug. Its lead programme has been tested in roughly 100 patients across multiple early-stage trials. On Sunday, UCB, the Brussels-listed pharmaceutical company, agreed to buy it for up to $2.2bn. That kind of price for that kind of biotech needs an explanation, and the explanation, in 2026, has a name: T-cell engagers…