A Food and Drug Administration advisory panel gave the go-ahead Wednesday to a new cholesterol-lowering drug from Amgen Inc. for patients with dangerously high cholesterol. The drug, Repatha, appears to be effective at lowering cholesterol, but long-term results are still needed to evaluate its overall benefit. An Amgen-sponsored study on the drug’s long-term results will not be complete until 2017. The FDA often follows the panel’s advice but is not required to do so.