Seattle Genetics, Inc., a biotechnology company focused on the development and commercialization of innovative antibody-based therapies for the treatment of cancer, presented data from two ongoing phase 1 clinical trials evaluating SGN-CD19A, an antibody-drug conjugate (ADC) in development for the treatment of B-cell malignancies, including non-Hodgkin lymphoma (NHL) and acute lymphoblastic leukemia (ALL), at the 56th American Society of Hematology (ASH) Annual Meeting and Exposition taking place in San Francisco, CA.
SGN-CD19A is an ADC targeting CD19, a protein expressed uniformly on almost all B-cell malignancies. The ADC is designed to be stable in the bloodstream and release its cytotoxic agent upon internalization into CD19-expressing cells. This approach is intended to spare non-targeted cells and thus reduce many of the toxic effects of traditional chemotherapy while enhancing antitumor activity.
“Aggressive B-cell malignancies are difficult diseases to treat, especially in the second- and third-line settings,” said Jonathan Drachman, M.D., chief medical officer and executive vice president, research and development at Seattle Genetics. “The data presented at ASH from two ongoing phase 1 clinical trials demonstrate encouraging antitumor activity with SGN-CD19A in patients with recurrent diffuse large B-cell lymphoma and acute lymphoblastic leukemia. The activity and safety profile, particularly multiple objective responses observed without significant myelosuppression or neuropathy typically associated with cancer treatment, supports the evaluation of SGN-CD19A in combination with standard of care regimens in the relapsed diffuse large B-cell lymphoma setting where improved outcomes are urgently needed. We look forward to initiating a randomized phase 2 trial evaluating SGN-CD19A in this setting in 2015.”
Data were reported from 52 patients with relapsed or refractory NHL, including 45 patients with diffuse large B-cell lymphoma (DLBCL), three patients with grade 3 follicular lymphoma and four patients with mantle cell lymphoma. Of the 52 patients, 30 patients (58 per cent) were refractory to their last therapy and 22 patients (42 per cent) were relapsed. Fourteen patients (27 per cent) had received a prior autologous stem cell transplant. The median age of patients was 65 years.
The primary endpoints of the ongoing clinical trial are to estimate the maximum tolerated dose and to evaluate the safety of SGN-CD19A. In addition, the trial is evaluating antitumor activity, pharmacokinetics, progression-free survival and overall survival. In this dose-escalation study, patients receive SGN-CD19A on an every three week schedule. Patients with stable disease or better are eligible to continue treatment with SGN-CD19A. Key findings in a poster presentation by Craig Moskowitz, M.D. Clinical Director, Division of Hematologic Oncology, Memorial Sloan Kettering Cancer Center, include:
The maximum tolerated dose was not exceeded after escalating to 6 milligrams per kilogram (mg/kg) every three weeks. In addition, evaluation of an every six week dosing schedule is underway and enrollment is ongoing.
Of the 51 patients evaluable for response, 18 patients (35 per cent) achieved an objective response, including 10 patients (20 percent) with a complete remission and eight patients (16 per cent) with a partial remission. Thirteen patients (25 per cent) achieved stable disease and 20 patients (39 per cent) had disease progression.
Antitumor activity appeared to be higher in relapsed patients. Of the 22 relapsed patients, 12 patients (55 per cent) achieved an objective response, including seven patients (32 per cent) with a complete remission and five patients (23 per cent) with a partial remission. Six patients (27 per cent) achieved stable disease and four patients (18 per cent) had disease progression.
The most common adverse events of any grade occurring in more than 25 percent of patients were blurred vision (60 per cent), dry eye (46 per cent), fatigue (38 percent), constipation (33 per cent) and keratopathy (31 per cent). Most ocular symptoms were Grade 1/2. The majority of patients with Grade 3 or 4 ocular symptoms and/or corneal findings experienced improvement and/or resolution at last follow-up. Ocular symptoms and corneal findings were managed with steroid eye drop treatment and dose modifications.
Interim Analysis of a Phase 1 Study of the Antibody-Drug Conjugate SGN-CD19A in Relapsed or Refractory B-Lineage Acute Leukemia and Highly Aggressive Lymphoma.
In this phase 1 trial, adult and pediatric patients with relapsed or refractory B-lineage ALL and highly aggressive lymphoma, including B-cell lymphoblastic lymphoma (LBL) and Burkitt lymphoma were enrolled. Data were reported from 51 adult patients. The median age of adult patients was 43 years and the median number of prior systemic therapies was two, with 14 patients (27 per cent) having received a prior allogeneic stem cell transplant.
The primary endpoints of the ongoing clinical trial are to estimate the maximum tolerated dose and to evaluate the safety of SGN-CD19A. In addition, the trial is evaluating antitumor activity, pharmacokinetics, progression-free survival and overall survival. In this dose-escalation study, patients received SGN-CD19A at either 0.3 to 2.3 mg/kg weekly or 4 to 6 mg/kg every three weeks. Key findings presented by Amir Fathi, M.D., Massachusetts General Hospital, include:
At the time of data analysis, dose escalation is ongoing. Safety analysis included data from 51 patients, including 18 patients treated every three weeks and 33 patients treated weekly.
Of the 14 ALL and LBL adult patients evaluable for response treated every three weeks, five patients (36 per cent) achieved an objective response, including four patients (29 per cent) with a complete remission and one patient (seven per cent) with a partial remission. Eight patients (57 per cent) achieved stable disease and one patient (seven per cent) had disease progression.
Of the 29 ALL and LBL adult patients evaluable for response treated with weekly dosing, six patients (20 per cent) achieved an objective response, including five patients (17 per cent) with a complete remission and one patient (three per cent) with a partial remission. Ten patients (34 per cent) achieved disease stabilization and 13 patients (45 per cent) had disease progression.
The most common adverse events of any grade occurring in 25 percent or more of adult patients treated every three weeks (18 patients) and weekly (33 patients), respectively, were fever (56 and 55 per cent), chills (33 and 56 per cent), fatigue (33 and 55 per cent), headache and nausea (28 and 55 per cent), blurred vision (39 and 36 per cent), vomiting (28 and 42 per cent) and febrile neutropenia (28 and 33 per cent).
Symptoms related to keratopathy were reported in 27 patients. All symptoms were Grade 1/2; no Grade 3 symptoms were reported. The most common symptoms were blurred vision, dry eye and photophobia. Grade 3 or 4 keratopathy was reported in 10 patients and the majority had experienced improvement and/or resolution at last follow-up. Ocular symptoms and corneal findings were managed with steroid eye drop treatment and dose modifications. Prophylactic eye drops were instituted early in the trial and appear to reduce the severity of corneal events in the weekly treatment schedule.
The SGN-CD19A phase 1 clinical trials are ongoing and additional data from both studies, including the impact of alternative dosing strategies, are planned in 2015. The company plans to initiate a randomized phase 2 trial evaluating SGN-CD19A in combination with R-ICE chemotherapy for second-line DLBCL during 2015. More information about the phase 1 SGN-CD19A clinical trials, including enrolling centers, is available by visiting www.clinicaltrials.gov.
SGN-CD19A is an ADC targeting CD19, a protein expressed broadly on B-cell malignancies. SGN-CD19A is comprised of an anti-CD19 monoclonal antibody linked to a synthetic cell-killing agent, monomethyl auristatin F (MMAF). The ADC is designed to be stable in the bloodstream, and to release its cytotoxic agent upon internalization into CD19-expressing tumor cells. This approach is intended to spare non-targeted cells and thus reduce many of the toxic effects of traditional chemotherapy while enhancing the antitumor activity.
Acute lymphoblastic leukemia, also called acute lymphocytic leukemia or ALL, is an aggressive type of cancer of the bone marrow and blood that progresses rapidly without treatment. In ALL, lymphoblasts, which are malignant, immature white blood cells, multiply and crowd out normal cells in the bone marrow. ALL is the most common type of cancer in children. According to the American Cancer Society, approximately 6,000 people were diagnosed with ALL during 2014 and more than 1,400 died from the disease.
Lymphoma is a general term for a group of cancers that originate in the lymphatic system. There are two major categories of lymphoma: Hodgkin lymphoma and NHL. NHL is further categorized into indolent (low-grade) or aggressive, including DLBCL. DLBCL is the most common type of non-Hodgkin lymphoma. According to the American Cancer Society, more than 70,000 cases of non-Hodgkin lymphoma were to be diagnosed in the United States during 2014 and nearly 19,000 people would die from the disease.