On December 6, 2018 SELLAS Life Sciences Group, Inc. (Nasdaq: SLS) ("SELLAS" or the "Company"), a clinical-stage biopharmaceutical company focused on the development of novel cancer immunotherapies for a broad range of cancer indications, reported additional data on patterns of clinical relapses (including organ or site of recurrence), as well as results from a preplanned secondary efficacy analysis across various predefined subgroups from the prospective, randomized, single-blinded, controlled Phase 2b independent investigator-sponsored clinical trial of the combination of trastuzumab (Herceptin) +/- nelipepimut-S (NeuVax, NPS) targeting HER2 low-expressing breast cancer patient cohorts at the 41st San Antonio Breast Cancer Symposium (SABCS) in San Antonio, TX (Press release, Sellas Life Sciences, DEC 6, 2018, View Source [SID1234531928]).

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These new data show a decrease in the total number of clinically detectable relapses with the combination of NPS + trastuzumab (7.5%) vs. trastuzumab alone (27.3%), p-value 0.004, which represents a 72.5% relative reduction in risk of relapse across time with a median follow up of 26.1 months in favor of the combination arm. Results from a planned analysis (log-rank) of the difference in disease free survival (DFS) outcomes between the two arms of the study in prespecified TNBC patient subgroups (patients who received neoadjuvant chemotherapy, expressed lower HER2, were 51 years or older, or had AJCC 7th Edition stage I/II TNBC), showed a clinically meaningful and statistically significant effect (p-value range: 0.004 – 0.014) in these subgroups in favor of the NPS plus trastuzumab combination arm. There was an average decrease of 84.2% in the relative risk of relapse or death at 24 months across these four subgroups of TNBC patients treated with NPS plus trastuzumab vs trastuzumab alone. The full data are summarized in the table below:

Comparison between NPS + trastuzumab vs. trastuzumab arms
Patient subgroups within the TNBC cohort Hazard Ratio (HR) HR 95% Confidence Interval P-value
(difference in favor of NPS + trastuzumab) Decrease in relative risk of relapse or death at 24 mos. (in favor of NPS + trastuzumab)
Received Neoadjuvant Chemotherapy 0.226 0.063 – 0.815 0.013 78.1%
Harbored BC with HER2 IHC 1+ expression level 0.178 0.038 – 0.837 0.014 81.3%
Aged ≥ 51 years 0.144 0.031 – 0.656 0.004 77.4%
AJCC 7 Stage I/II at diagnosis Incalculable* N/A 0.006 100%
*no DFS events occurred in AJCC 7 stage I/II TNBC patients treated with NPS plus trastuzumab.

"These new data provide insights on the pattern of clinically detectable relapses across various sites/organs, as well as add to our knowledge of the specific potential benefit distribution within the TNBC cohort. The results in four predefined TNBC subgroups inform us of the types of TNBC patients with residual disease after neoadjuvant chemotherapy who may potentially benefit when treated with NPS plus trastuzumab in the adjuvant setting. As previously announced, we are on track to meet with the U.S. Food and Drug Administration this month on the most expeditious and appropriate development path for NPS in TNBC," said Nicholas J. Sarlis, MD, PhD, Executive Vice President and Chief Medical Officer of SELLAS.

"We are very pleased with the results of these new analyses which indicate that the NPS plus trastuzumab combination – when given in the adjuvant setting after frontline therapy – could potentially improve outcomes across specific predefined subgroups of patients with early-stage TNBC, an aggressive subtype of breast cancer. The clinically meaningful and statistically significant decrease in the frequency of clinically detectable relapses – with a median follow-up of over 26 months – indicates a high degree of internal consistency," commented Elizabeth A. Mittendorf, MD, PhD, Rob and Karen Hale Distinguished Chair in Surgical Oncology, Director of Research, Breast Surgical Oncology Brigham and Women’s Hospital, Director, Breast Immuno-Oncology Program Dana-Farber/Brigham and Women’s Cancer Center, and the Principal Investigator of the Phase 2b study. "The data presented today are consistent with the previously reported beneficial effect seen in the TNBC cohort at large and are consistent with the immunobiological mechanism of action of nelipepimut-S."

Herceptin is a registered trademark of Genentech, Inc. and is not a trademark of SELLAS. The manufacturer of this brand is not affiliated with and does not endorse SELLAS or its products.

SABCS Presentation Information

Date and Time: Thursday, December 6, 2018; 8:00 – 10:00 am ET
Poster Session 2: Treatment: Immunotherapy (clinical)
Poster Hall Location: Hall 1
Abstract ID: P2-09-01
Title: Subgroups analysis of a multicenter, prospective, randomized, blinded phase 2b trial of trastuzumab + nelipeptimut-S (NeuVax) vs. trastuzumab for prevention of recurrence in breast cancer patients

About SABCS

The mission of the SABC Symposium (SABCS) is to provide state-of-the-art information on breast cancer research. Since 2007, the SABCS has been jointly sponsored by the Cancer Therapy & Research Center (CTRC) at the University of Texas Health Science Center – San Antonio, the Baylor College of Medicine and the American Association for Cancer Research (AACR) (Free AACR Whitepaper).