Drug discovery and development company Summit Therapeutics has received approval from the US and Food Drug Administration (FDA) for its novel antibiotic.The FDA granted fast-track designation for the SMT19969 antibiotic which treats both duchenne muscular dystrophy and C. difficile infection (CDI).There is currently no cure for duchenne muscular dystrophy, a fatal muscle-wasting disease that affects around 1 in 3,500 males births.Fast-track designation is awarded to expedite the development and regulatory review of drugs intended to treat serious or life-threatening conditions and that demonstrate the potential to address unmet medical needs, the company explained.Chief executive Glyn Edwards said: "Fast-track designation recognises the serious healthcare threat posed by C. difficile due to a high rate of disease recurrence, the key clinical issue in treating CDI, and underscores the importance of developing a candidate like SMT19969, which has significant potential to address both the initial infection and recurrence".N+1 Singer analysts said they remain upbeat about Summit's future prospects, adding the 245p intrinsic value per share could increase to 747p if its study successfully progresses to pivotal trials."The second half of the year promises to generate significant news flow and we believe the potential upside in Summit is substantial," the broker added.Shares rose 0.75% to 134.5p on Wednesday at 12:04.