ImmunoGen, Inc.
Dec 6, 2014

ImmunoGen, Inc. Announces Encouraging IMGN529 Clinical Data Presented at 56th ASH Annual Meeting and Exposition

SAN FRANCISCO--(BUSINESS WIRE)-- ImmunoGen, Inc. (NASDAQ: IMGN), a biotechnology company that develops novel anticancer therapeutics using its antibody-drug conjugate (ADC) technology, today announced the presentation of encouraging clinical findings with its IMGN529 experimental therapy for B-cell malignancies at the American Society of Hematology (ASH) annual meeting (abstract #1760). These include objective responses at doses that were generally well tolerated.

ImmunoGen's IMGN529 is a potential new treatment for DLBCL and other non-Hodgkin lymphoma (NHL) subtypes. An ADC, it comprises an antibody that targets CD37, found on B-cell malignancies, with the potent cancer cell-killing agent, DM1, attached. The antibody serves to deliver the DM1 specifically to B cells to kill them and, based on preclinical research, also contributes anticancer activity.1

IMGN529 is currently in the dose-finding portion of a Phase I clinical trial, which assesses increasing doses of this experimental therapy in new groups of patients with relapsed/refractory NHL. Findings with the first doses evaluated were reported previously.2

Clinical Data Presented

The IMGN529 dose levels evaluated to date range from 0.1 to 1.4 mg/kg, administered once every three weeks. Its MTD has not yet been established, and evaluation of the 1.4 mg/kg level is ongoing.

Twenty four (24) of the 33 patients enrolled to date were evaluable for efficacy. Ten evaluable patients had DLBCL, which had been heavily pretreated, and four (40%) of these patients had an objective response: one had a complete response (CR) and three had partial responses (PRs). The CR and one of the PRs were among patients treated with 1.0 mg/kg, the highest IMGN529 dose level to complete evaluation to date. Both of these patients had received multiple prior treatments, including autologous stem cell transplant (ASCT). Ten of the 24 evaluable patients had follicular lymphoma and one of these patients also had a PR. This patient, too, had received multiple treatments including ASCT.

As reported previously, an early onset, transient drop in neutrophil counts was seen in several patients receiving IMGN529 at low doses.2 This was believed to be due to a redistribution of the neutrophils - induced by antibody-mediated cytokine release - rather than to bone marrow suppression; subsequent preclinical research supports this hypothesis (see abstract #3119).

With the addition of peri-infusional steroids to the treatment protocol, the incidence and severity of neutropenia decreased markedly and dose escalation resumed. As reported previously, the first patients treated with 1.0 mg/kg had delayed onset neutropenia or febrile neutropenia.2 G-CSF was subsequently added to the treatment protocol and there have been no new reports of febrile neutropenia at doses of 1.0 or 1.4 mg/kg; the one incidence of high grade neutropenia seen with 1.4 mg/kg was of short (2 day) duration.

Hematologic side effects are not unexpected in such heavily pretreated patients. Other frequent side effects were fever, fatigue, nausea, and diarrhea, which were typically Grade 1/2.

"It is encouraging that patients with such heavily pretreated disease responded to IMGN529," commented Dr. Charles Morris, EVP and Chief Development Officer. "We are particularly pleased with the responses seen in the patients with diffuse large B-cell lymphoma given the limited treatment options for such patients today, and look forward to advancing IMGN529 into disease-specific testing in 2015."

About Diffuse Large B-cell Lymphoma (DLBCL)

More than 70,000 people will be diagnosed with non-Hodgkin lymphoma (NHL) in the US in 2014.3 DLBCL is an aggressive lymphoma that represents approximately one third of the new NHL cases diagnosed annually.3

About ImmunoGen, Inc.

ImmunoGen, Inc. develops targeted anticancer therapeutics. The Company's ADC technology uses tumor-targeting antibodies to deliver an ImmunoGen cell-killing agent specifically to cancer cells; the Company has also developed antibodies with anticancer activity of their own. The first product with ImmunoGen's ADC technology is Roche's Kadcyla®. ImmunoGen has three wholly owned product candidates in clinical testing with additional compounds in clinical testing through the Company's partnerships with Amgen, Bayer HealthCare, Biotest and Sanofi. More information about ImmunoGen can be found at

Kadcyla® is a registered trademark of Genentech, a member of the Roche Group.

1Deckert et al. Blood, 2013 Nov 14; 122(20):3500-10.

2ASCO annual meeting 2014; abstract #8526.

3American Cancer Society (2014), Cancer Facts & Figures.

This press release includes forward-looking statements. For these statements, ImmunoGen claims the protection of the safe harbor for forward-looking statements provided by the Private Securities Litigation Reform Act of 1995. It should be noted that there are risks and uncertainties related to the development of novel anticancer products, including IMGN529, including risks related to preclinical and clinical studies, their timings and results. A review of these risks can be found in ImmunoGen's Annual Report on Form 10-K for the fiscal year ended June 30, 2014 and other reports filed with the Securities and Exchange Commission.

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ImmunoGen, Inc.
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Source: ImmunoGen, Inc.

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