Senator Charles Grassley told the SEC he is concerned about a big jump in Vertex Pharmaceuticals’ stock price on May 7, after the release of overstated test data for a drug it is developing. The Cambridge firm’s stock rose 55 percent based on results from a clinical trial that Vertex later said were flawed. Before that, five executives and two directors cashed in stock and options worth millions. A spokesman declined to comment on the letter, but said Vertex moved quickly to disclose the new test data.