June 1 (Reuters) - Fulcrum Therapeutics FULC.O said on Monday it would stop developing its experimental sickle-cell disease drug after the U.S. Food and Drug Administration raised cancer-risk concerns, which left no viable regulatory path for the treatment.

The drug developer's shares slumped nearly 50% in extended trading.

• The drug, pociredir, was being developed as an oral treatment for sickle-cell disease, an inherited blood disorder that can cause pain, anemia, organ damage and reduced life expectancy.

• Fulcrum said the FDA concerns were tied to secondary blood cancers seen with Ipsen's IPN.PA cancer drug, Tazverik, which was withdrawn globally in March.

• The company said it submitted information to the FDA supporting the position that mechanistic differences between the two drugs' target were relevant to the benefit-risk assessment.

• The FDA, however, concluded that any drug that targets the protein PRC2 carries risk.

• "We arrived at this decision after discussion with the FDA, and despite robust elevations in fetal hemoglobin seen with pociredir and the potential for clinical benefit, we do not see a path forward with pociredir," said Fulcrum CEO Alex Sapir.

• Fetal hemoglobin is a form of hemoglobin linked to clinical benefit in sickle-cell disease.

• Fulcrum will explore options including a merger, acquisition, business combination or other transaction, and has initiated efforts to cut operating expenses and preserve cash.