Waltham, MA-based ImmunoGen ($IMGN) is reporting early signs of success for its armed antibody mirvetuximab soravtansine (IMGN853), which sent its stock up 19% in early trading on Monday. One of the pioneers in the development of antibody drug conjugates, ImmunoGen has been working on a new ADC for FRα-positive platinum-resistant ovarian cancer which zeroes in on this cancer and then drops a highly toxic payload on the target. Among 17 evaluable patients in their early study of this therapy, 9--or 53%--had an objective response to the therapy and 6 of them were still responding at the time of the data cutoff. And Charles Morris, the company's chief development officer, says that the biotech has a shot at a near-term application to the FDA. "We're preparing to initiate a Phase II trial in late 2015 that will assess this ADC as a single-agent treatment for patients with FRα-positive platinum-resistant ovarian cancer. It is possible that this trial could be used for registration in this patient population," Morris noted in a statement. Release