Drugmaker Pfizer Inc. has signed a deal with an UN-backed group to allow other manufacturers to make its experimental COVID-19 pill, a move that could make the treatment available to more than half of the world's population. In a statement issued Tuesday, Pfizer said it would grant a license for the antiviral pill to the Geneva-based Medicines Patent Pool, which would let generic drug companies produce the pill for use in 95 countries, making up about 53% of the world's population.