Seattle Genetics Presents Updated Phase 1 Data for Ladiratuzumab Vedotin (SGN-LIV1A) in Patients with Triple Negative Breast Cancer at 2017 San Antonio Breast Cancer Symposium

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BOTHELL, WA, USA I December 7, 2017 I Seattle Genetics, Inc. (NASDAQ: SGEN) today announced updated data from an ongoing phase 1 clinical trial evaluating ladiratuzumab vedotin in patients with metastatic triple negative breast cancer (TNBC) at the 2017 San Antonio Breast Cancer Symposium (SABCS), taking place December 5-9, 2017. Ladiratuzumab vedotin is an investigational antibody-drug conjugate (ADC) designed to deliver a potent and clinically validated cell-killing agent, monomethyl auristatin E (MMAE), to cancer cells which express the protein LIV-1. LIV-1 is expressed on multiple solid tumors including breast, prostate, melanoma, ovarian, uterine, and cervical cancers.

“Overall, the phase 1 results we’ve presented at SABCS confirm previous findings that single-agent treatment with ladiratuzumab vedotin was generally well-tolerated and showed encouraging antitumor activity in patients with heavily-pretreated metastatic TNBC,” said Robert Lechleider, M.D., Senior Vice President, Clinical Development at Seattle Genetics. “We continue to evaluate ladiratuzumab vedotin monotherapy in TNBC, with planned combination studies in earlier lines of treatment, demonstrating our overarching commitment to improve the health of women with this devastating disease.”

Findings from this ongoing phase 1 study of ladiratuzumab vedotin in patients with metastatic breast cancer were last presented at the 2016 SABCS. The updated results presented today in a spotlight session describe the safety, tolerability, and antitumor activity of ladiratuzumab vedotin in 28 additional patients with TNBC.

Phase 1 Study of the Antibody-Drug Conjugate Ladiratuzumab Vedotin (SGN-LIV1A) in Patients with Heavily Pretreated Triple-Negative Metastatic Breast Cancer (Poster# PD3-14, Poster Session - Novel Drugs / Predicting Response for HER2+ Breast Cancer at 7:00 – 9:00 a.m. CT on Thursday, December 7, 2017)

A total of 81 patients with LIV-1-expressing metastatic breast cancer were treated with ladiratuzumab vedotin monotherapy given every three weeks. Patients enrolled in the study had received a median of four prior systemic metastatic therapies. Of these patients, 63 were diagnosed with TNBC and 18 had hormone receptor-positive / human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer. At the completion of dose escalation at doses ranging from 0.5 to 2.8 milligrams per kilogram (mg/kg), TNBC expansion cohorts were opened at 2.0 and 2.5 mg/kg to further evaluate safety and antitumor activity of ladiratuzumab vedotin in metastatic TNBC patients. Based on efficacy and safety, the recommended dose is 2.5 mg/kg with a maximum dose of 200 mg per cycle.

Key findings in this heavily pre-treated patient population were presented by Dr. Jennifer Specht, Seattle Cancer Care Alliance and include:

  • Among the 60 efficacy-evaluable patients with metastatic TNBC, the objective response rate (ORR) was 25 percent, representing all partial responses (PR). The clinical benefit rate (CBR) was 28 percent. CBR is defined as patients achieving complete response (CR) or PR of any duration, plus patients achieving stable disease (SD) lasting at least 24 weeks. Of the 17 efficacy-evaluable patients treated at the recommended dose, 29 percent achieved an objective response (confirmed and unconfirmed), and the CBR was 29 percent.
  • The median progression-free survival (PFS) and median duration of response (DOR) for patients treated across all dose levels were 11 weeks and 13.3 weeks, respectively. In 19 patients treated at the recommended dose, the median PFS was 12.1 weeks, and the median DOR was 17.4 weeks.
  • At the recommended dose, ladiratuzumab vedotin was generally well-tolerated and most adverse events were Grade 1/2.
  • Of the 81 patients treated in the study, peripheral neuropathy events occurred in 16 patients (19.8 percent) and were generally low grade (Grades 1/2) and manageable. Seven patients discontinued treatment due to adverse events.
  • Grade 3/4 adverse events included neutropenia and anemia. The Grade 3/4 incidence of neutropenia at the 2.5 mg/kg dose was 38.7 percent. As previously reported, two patients experienced febrile neutropenia, and there was one treatment-related death due to presumed sepsis among patients who received doses greater than 200 mg. No other treatment-related deaths occurred in the study.
  • Enrollment continues for patients with metastatic TNBC at the recommended dose of 2.5 mg/kg, with a maximum dose of 200 mg per cycle.

Additional details about this spotlight poster presentation (Poster PD3-14) are available here. More information about the ladiratuzumab vedotin phase 1 clinical trial in TNBC, including enrollment centers, is available by visiting www.clinicaltrials.gov.

About Triple Negative Breast Cancer

Breast cancer is the most common cancer among women in the United States, excluding some forms of skin cancer. Of the more than 250,000 new cases expected in the United States this year, about 15 to 20 percent will be TNBC, which has a particularly poor prognosis. Breast cancers are commonly categorized by the expression (or lack thereof) of three proteins, which include the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). TNBC lacks expression of these three breast cancer-associated proteins that serve as key therapeutic targets. About one-third of breast cancer patients will eventually develop recurrent or metastatic disease, and current therapies for metastatic TNBC only delay progression. New treatment approaches are needed to improve outcomes for women with TNBC, where there are currently no available targeted therapies.

About Ladiratuzumab Vedotin

Ladiratuzumab vedotin is a novel investigational ADC targeted to LIV-1 protein utilizing Seattle Genetics’ proprietary ADC technology. Most metastatic breast cancers express LIV-1, which also has been detected in a number of other cancers, including melanoma, prostate, ovarian, uterine, and cervical cancers. Ladiratuzumab vedotin consists of a LIV-1-targeted monoclonal antibody linked to a potent microtubule-disrupting agent, monomethyl auristatin E (MMAE) by a protease-cleavable linker, using the same technology as ADCETRIS (brentuximab vedotin). This novel ADC agent is designed to bind to LIV-1 on cancer cells and release the cell-killing agent into target cells upon internalization. Ladiratuzumab vedotin may also cause antitumor activity through other mechanisms, including activation of an immune response. Seattle Genetics currently has four clinical studies underway or planned for ladiratuzumab vedotin in breast cancer with a focus on TNBC.

About Seattle Genetics

Seattle Genetics is an innovative biotechnology company dedicated to improving the lives of people with cancer through novel antibody-based therapies. The company’s industry-leading antibody-drug conjugate (ADC) technology harnesses the targeting ability of antibodies to deliver cell-killing agents directly to cancer cells. Seattle Genetics commercializes ADCETRIS® (brentuximab vedotin) for the treatment of several types of CD30-expressing lymphomas. The company is also advancing a robust pipeline of novel therapies for solid tumors and blood-related cancers designed to address significant unmet medical needs and improve treatment outcomes for patients. More information can be found at www.seattlegenetics.com and follow @SeattleGenetics on Twitter.

SOURCE: Seattle Genetics

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