Researchers have developed a new drug that protects animals' bone marrow and gastrointestinal cells from being destroyed by radiation therapy, without reducing radiation’s effectiveness against tumor cells. Although radiation is an important weapon against cancers, drugs that limit radiation’s devastating effects on healthy cells are needed to reduce the potentially severe side effects of the therapy. The new drug CBLB502, tested in mice and monkeys, works by activating a well-known molecular pathway that some cancer cells use to stave off cell death, the researchers say.