In January 1905, the world’s largest gem-quality rough diamond was discovered at the Premier No. 2 mine in Cullinan, modern-day South Africa, and cut into several polished gemstones, some of which became part of Great Britain’s Crown Jewels. Cullinan Oncology LLC hopes to imitate that feat by building a portfolio of oncology assets from one-off opportunities whose profile makes them unsuitable for single-asset companies.