Irvine-based Spectrum Pharmaceuticals, a biopharmaceuticals firm focused on hematology and oncology, said today that it has named George Tidmarsh, M.D., Ph.D., as Senior Vice President and Chief Scientific Officer. Tidmarsh was the founder of Horizon Pharma and Threshold Pharmaceuticals, and also has served at Coulter Pharmaceuticals, Sequus Pharmaceuticals, Gilead Sciences, Systemix, and Metronome Therapeutics. The firm said the appointment would add significant expertise in radioimmunotherapy and other cancer treatments to the company.