Seattle Genetics (SGEN), Agensys Present Updated ASG-22ME, ASG-15ME Data at ESMO 2016

October 7, 2016 9:02 AM EDT

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Seattle Genetics, Inc. (Nasdaq: SGEN) and Agensys, an affiliate of Astellas, presented updated clinical data for enfortumab vedotin (ASG-22ME) and ASG-15ME at the European Society for Medical Oncology (ESMO) Congress being held October 7-11, 2016 in Copenhagen, Denmark. Enfortumab vedotin and ASG-15ME are investigational antibody-drug conjugates (ADCs) that target the cell surface proteins Nectin-4 and SLITRK6, respectively. The clinical data for both agents continue to demonstrate overall response rates in patients with previously treated metastatic urothelial cancer, including those with prior checkpoint inhibitors. Safety and recommended phase 2 doses were also presented for both programs. While both phase 1 studies will continue to enroll patients, the companies plan to advance enfortumab vedotin and discuss next steps with regulatory agencies. Evaluation of next developmental steps for ASG-15ME is ongoing.

“We are pleased to advance the enfortumab vedotin development program for patients with metastatic urothelial cancer. These patients are in dire need of new treatment options as their prognosis is grim, with a five-year survival rate of about 15 percent,” said Jonathan Drachman, M.D., chief medical officer and executive vice president, Research and Development at Seattle Genetics. “The antitumor activity and safety profile of enfortumab vedotin in heavily pretreated metastatic patients is encouraging, particularly in those patients who have failed both platinum-based chemotherapy and checkpoint inhibitors. We look forward to discussions with regulatory agencies.”

“Both enfortumab vedotin and ASG-15ME hold potential promise for metastatic urothelial cancer patients,” said Steven Benner, M.D., senior vice president, therapeutic area head for oncology development, Astellas. “As we consider our next steps in these two development programs, we also pause to thank the patients, caregivers and clinical investigators who participate in these clinical trials for the important role they play in advancing the science of cancer care.”

Interim data from two phase 1 dose-escalation studies of enfortumab vedotin and ASG-15ME monotherapy in patients with metastatic urothelial cancer will be presented at the ESMO Congress during poster sessions on Sunday, October 9, 2016. The respective clinical trial data showed that each agent had antitumor activity in patients previously treated with platinum-based chemotherapy, checkpoint inhibitors, taxanes and those with liver metastases. Enfortumab vedotin and ASG-15ME were generally well-tolerated, and phase 1 enrollment is ongoing with both agents, with an increased focus on checkpoint-inhibitor treated patients to further understand safety and activity in this population. Detailed findings are summarized below:

Interim Analysis of a Phase 1 Dose Escalation Trial of ASG-22CE (ASG-22ME; enfortumab vedotin), an Antibody-Drug Conjugate (ADC) in Patients (Pts) with Metastatic Urothelial Cancer (mUC) (Abstract #788P, poster presentation on Sunday, October 9, 2016)

Data were reported from 58 patients with metastatic urothelial cancer having a median age of 67 years. Of these patients, 56 patients (97 percent) had undergone treatment with a platinum-based chemotherapy regimen and 20 patients (35 percent) had progressed on or after treatment with checkpoint inhibitors. Thirty-six patients (62 percent) had received two or more prior systemic therapies. The primary endpoints of the ongoing clinical trial are to evaluate pharmacokinetics and safety of enfortumab vedotin as a monotherapy at escalating doses of 0.5 to 1.25 milligrams per kilogram (mg/kg) weekly for three of every four week cycles. In addition, the trial is evaluating antitumor activity, objective response rate and disease control rate. Key findings include:

  • Of the 49 patients evaluable for response, 18 patients (37 percent) had an objective response, including one patient (two percent) who achieved a complete response and 17 patients (35 percent) who achieved a partial response. The preliminary estimate of median progression-free survival is 16.6 weeks.
  • The recommended phase 2 dose is 1.25 mg/kg. In 17 patients treated at the 1.25 mg/kg dose level, 10 patients (59 percent) had a partial response. Disease control was achieved for 14 patients (82 percent), defined as achieving complete response, partial response or stable disease.
  • In the 16 patients across dose levels who had previously been treated with checkpoint inhibitors, six patients (38 percent) achieved a partial response. At the recommended phase 2 dose, four out of seven patients (57 percent) previously treated with checkpoint inhibitors achieved a partial response.
  • In the 12 patients whose cancer had metastasized to the liver, which typically has a poor prognosis, five patients (42 percent) achieved an objective response. Of 20 patients previously treated with taxanes, eight (40 percent) achieved an objective response.
  • The most common treatment related adverse events of any grade occurring in 20 percent or more of patients were pruritis (31 percent), fatigue (30 percent), diarrhea (29 percent), nausea (28 percent), rash (26 percent) and alopecia (21 percent).
  • Eight of 19 patients (42 percent) experienced a rash at the recommended phase 2 dose and none of these patients required dose modification or discontinued therapy as a result.
  • Enrollment is ongoing at 1.25 mg/kg and the study has been amended to include a checkpoint inhibitor-treated cohort to further understand safety and activity in this population.

Interim Analysis of a Phase 1 Dose Escalation Trial of the Antibody-Drug Conjugate (ADC) AGS15E (ASG-15ME) in Patients (Pts) with Metastatic Urothelial Cancer (mUC) (Abstract #780PD, poster presentation with discussion on Sunday, October 9, 2016)

Data were reported from 54 patients with metastatic urothelial cancer having a median age of 64 years. Of these patients, 52 patients (96 percent) had previously undergone treatment with a platinum-based chemotherapy regimen and 17 patients (32 percent) had progressed on or after treatment with checkpoint inhibitors. Thirty patients (56 percent) had received two or more prior systemic therapies. The primary endpoints of the ongoing clinical trial are to evaluate the pharmacokinetics and safety of ASG-15ME as a monotherapy at escalating doses of 0.1 to 1.25 mg/kg weekly for three of every four week cycles. In addition, the trial is evaluating antitumor activity, objective response rate and disease control rate. Key findings include:

  • Of the 48 patients evaluable for response, 18 patients (38 percent) had an objective response, including one patient (two percent) who achieved a complete response and 17 patients (35 percent) who achieved a partial response. The preliminary estimate of median progression-free survival is 16.1 weeks.
  • The recommended phase 2 dose is 1.0 mg/kg. In 20 patients treated at the 1.0 mg/kg dose level, 10 patients (50 percent) had an objective response, including one patient (five percent) who achieved a complete response and nine patients (45 percent) who achieved a partial response. Disease control was achieved for 14 patients (70 percent), defined as achieving complete response, partial response or stable disease.
  • Of the 14 patients across dose levels who had previously been treated with checkpoint inhibitors, six patients (43 percent) achieved a partial response. At the recommended phase 2 dose, three out of seven patients (43 percent) previously treated with checkpoint inhibitors achieved a partial response.
  • In the 13 patients whose cancer had metastasized to the liver, which typically has a poor prognosis, six patients (46 percent) achieved an objective response. Of 22 patients previously treated with taxanes, nine (41 percent) achieved an objective response.
  • The most common treatment related adverse events of any grade occurring in 20 percent or more of patients were fatigue (44 percent), nausea (22 percent) and decreased appetite (20 percent).
  • Fourteen patients (26 percent) experienced ocular adverse events and six patients (11 percent) developed ocular symptoms with corneal abnormalities at the recommended phase 2 dose. All events resolved with appropriate management.
  • Enrollment is ongoing at 1.0 mg/kg and the study has been amended to include a checkpoint inhibitor-treated cohort to further understand safety and activity in this population.

More information about these clinical trials, including enrolling centers, is available by visiting www.clinicaltrials.gov.



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