ImmunoGen presents first clinical data of IMGN853 at ASCO annual meeting

ImmunoGen, Inc. (Nasdaq: IMGN), a biotechnology company that develops anticancer therapeutics using its Targeted Antibody Payload (TAP) ADC technology, today announced the presentation of the first clinical data with the Company's IMGN853 product candidate. The data are from the ongoing dose-finding portion of a Phase I clinical assessment of the compound, which is a potential treatment for many ovarian, endometrial, and non-small cell lung cancers, as well as other FRα-overexpressing cancers. The data are being presented (abstract #2573) at the American Society of Clinical Oncology (ASCO) annual meeting taking place in Chicago, IL.

“Preliminary evidence of activity has been seen in the dose-finding portion of this trial. We look forward to completing this part of the trial and beginning evaluation of IMGN853 in disease-specific patient populations.”

First Data from Dose-Finding Assessment

The dose-finding portion of this Phase I clinical trial is designed to establish the maximum tolerated dose of IMGN853 and to define its dose-limiting toxicity (DLT). Patients with any type of cancer known to overexpress IMGN853's FRα target are eligible for enrollment in this phase of the trial. Once the maximum tolerated dose is established, IMGN853 will be evaluated in patients with specific types of FRα-overexpressing cancers, with prescreening to ensure tumor levels of FRα-overexpression meet defined criteria.

At the time of data cutoff for presentation, 18 patients had received IMGN853 at doses ranging from 0.15 to 7.0 mg/kg. DLT, seen at 7.0 mg/kg, was reversible blurred vision with epithelial corneal changes. The patients assigned to this dose were reduced to 5.0 mg/kg, the second highest dose evaluated. Additional new patients are being treated with 5.0 mg/kg to further assess that dose.

While this assessment is designed to evaluate the safety of IMGN853 and establish its maximum tolerated dose, evidence of clinical activity is also identified. Activity started to be seen when dose levels reached 3.3 mg/kg and included:

• A patient with serous epithelial ovarian cancer assigned to treatment with IMGN853 at 3.3 mg/kg had a confirmed CA-125 response - a pronounced, sustained reduction in CA-125 levels - and stable disease lasting 18 weeks. This patient previously had received 12 other treatment regimens.
• A patient with serous endometrial cancer achieved a partial response (PR), awaiting confirmation, after four cycles of treatment with IMGN853; she also had a marked decrease in CA-125 levels. This patient previously had received two platinum-based regimens that included paclitaxel. She was assigned to treatment with IMGN853 at the 5.0 mg/kg dose level and continues on therapy.
• A patient with platinum-resistant, transitional cell ovarian cancer achieved a PR, awaiting confirmation, after two cycles of treatment with IMGN853. She also had a pronounced decrease in her CA-125 levels. She was assigned to receive IMGN853 at 7.0 mg/kg, experienced a DLT, and remains on study at 5.0 mg/kg.

All three of these patients had cancer that scored strongly positive for IMGN853's FRα target, as determined by well-established immunohistochemistry (IHC) assessment.

"We are highly encouraged by these initial clinical findings with IMGN853," commented Dr. Charles Morris, Executive Vice President and Chief Development Officer. "Preliminary evidence of activity has been seen in the dose-finding portion of this trial. We look forward to completing this part of the trial and beginning evaluation of IMGN853 in disease-specific patient populations."

ImmunoGen expects to begin the disease-specific, dose-expansion phase of this trial later this year. In that phase, IMGN853 will be evaluated in patients who have been prescreened for specific levels of FRα-overexpression and have either: (1) platinum-resistant ovarian cancer treated with three or fewer prior regimens; (2) relapsed/refractory ovarian cancer treated with less strictly defined prior therapies; or (3) adenocarcinoma non-small cell lung cancer. Addition of a cohort to assess IMGN853 for endometrial cancer is now also planned.

SOURCE ImmunoGen, Inc.