SELLAS Life Sciences Group, Inc. (NASDAQ: SLS) ("SELLAS" or the
“Company”), a late-stage clinical biopharmaceutical company focused
on developing novel cancer immunotherapies for a broad range of
indications, today announced promising updated clinical data and
initial immunobiological data from its Phase 1/2 clinical trial
with its lead asset, galinpepimut-S (GPS), the Company’s Wilms
Tumor-1 (WT1)-targeting peptide immunotherapeutic, in combination
with the checkpoint inhibitor pembrolizumab (Keytruda®).
Conducted under a Clinical Trial Collaboration and
Supply Agreement with Merck & Co., Inc., Kenilworth, N.J. USA
(known as MSD outside of the United States and Canada), the study
is investigating the combination of GPS and pembrolizumab in
treating patients diagnosed with second- or third-line WT1(+)
relapsed or refractory platinum-resistant, advanced metastatic
ovarian cancer. The WT1 antigen is one of the most widely expressed
cancer antigens in multiple malignancies and has been ranked by the
National Cancer Institute as the top priority among cancer antigens
for immunotherapy.
The study details are as follows:
- Eleven patients (median age: 63 years) who received at least
three GPS doses, the last of which was combined with pembrolizumab,
were evaluated for clinical responses and three of those patients
were also evaluated for immune responses.
- 66.7 percent of evaluable patients were refractory to or had
failed their second-line therapies, and 33.3 percent failed
third-line therapy or later.
- All enrolled patients (100 percent) were resistant to the
standard of care platinum-based therapy. Expected overall survival
for patients receiving standard of care platinum-based therapy is
nine to 12 months.
- Median overall survival among the patients in this trial is not
yet known as all patients are still alive at the time of the
analysis, which period of time exceeds nine months.
Disease Control Rate An ad hoc analysis of
clinical outcomes in the cohort of 11 patients shows a disease
control rate (DCR), the sum of overall response rate and rate of
stable disease, of 63.6 percent, with a median follow-up of 15.4
weeks. In December 2020, the Company reported initial data showing
a DCR of 87.5 percent in eight patients, with a median follow-up of
9.4 weeks. In this very difficult treatment-resistant patient
population, at the time of the follow-up analysis, median
progression-free survival (PFS) was 11.8 weeks. The landmark PFS
rate by log-rank analysis at six months (26 weeks) was 33
percent.
Analysis of the updated data, using a validated
immunohistochemistry assay during the eligibility screening period,
shows that the rate of WT1 ovarian tumor positivity in this patient
population remained high at approximately 63.6 percent. As of the
time of this analysis, all patients are alive, and five patients
(45.5 percent) are continuing to receive investigational therapy.
Enrollment for this study is ongoing, with a target of
approximately 20 total evaluable patients.
The safety profile of the GPS-pembrolizumab
combination was similar to that seen with pembrolizumab alone, with
the addition of only low-grade, temporary local reactions at the
GPS injection site, consistent with previously performed clinical
studies with GPS.
Immunobiological Data CD8+ and CD4+ T-lymphocytes
were isolated from peripheral blood mononuclear cells from three
patients from whom samples had been collected both at baseline and
at the time of the sixth GPS dose (i.e., 18 weeks after starting
investigational therapy). The T-cells were assayed ex-vivo for
immune responses against the pool of the four peptides that
comprise GPS using the validated assay intracellular cytokine
staining with fluorescence-activated single cell sorting (ICS-FACS)
(Scorpion Biological Services, San Antonio, Texas), with
appropriate positive and negative controls.
A total of five cytokine “channels” were used for
the analysis (i.e., interferon-g, TNF-a, interleukin-2, CD107a and
MIP-1b). The peptide re-challenge incubation period was seven days.
At the 18-week time point versus pre-vaccination baseline, the
assay demonstrated a relative increase in WT1-specific T-lymphocyte
frequencies in peripheral blood averaging +242 percent (range: +104
to +385 percent across five cytokines) for CD8+ and +80.5 percent
(range: +1 to +174 percent) for CD4+. There was also evidence of
polyfunctional T-cell activation (increases in secretion of >2
cytokines) in two out of three patients (66 percent).
“Considering the overall poor prognosis in this
particular clinical setting and based on the observed median PFS,
overall survival and DCR in this study, combining GPS with the PD1
inhibitor pembrolizumab appears to be clinically promising as
compared to bevacizumab-free salvage chemotherapy regimens and
without the toxicity burden associated with the latter,” said
Angelos Stergiou, M.D., Sc.D. h.c., President and CEO, SELLAS.
“Patients treated with GPS plus pembrolizumab also appear to
maintain a considerable degree of stable disease, as evidenced by
the median DCR of 63.6 percent – all evaluable patients are alive.
Continuing to review the clinical data will help us determine the
fundamental value of the combination approach to fighting this
disease. The initial trends are promising, and further maturity of
the data and studying additional patients will allow us to draw
more definitive conclusions regarding the clinical benefit. We
expect to perform another set of similar ad hoc clinical and
immunobiological analyses over the next six months as the study
progresses.”
“Based on this early data, it is encouraging to
see the induction of WT1-specific T-cell immune responses with the
administration of GPS in combination with pembrolizumab with a
validated complex ex-vivo immune response assay on peripheral blood
from patients with platinum-refractory metastatic ovarian cancer
who had undergone numerous prior therapies,” added Jeffrey S.
Weber, M.D., Ph.D.; Deputy Director of the Perlmutter Cancer Center
at New York University (NYU)-Langone Health; Co-Director of its
Melanoma Research Program Center; and Chair of SELLAS’ Scientific
Advisory Board. “Expansion of these results with data from
additional patients, as well as at time points longer than 18 weeks
(when such patient samples become available for testing), will be
key in getting a more comprehensive picture of the combination
immunotherapy’s biological effect.”
About Ovarian Cancer Ovarian
cancer is one of the most common gynecologic malignancies and the
fifth most frequent cause of cancer death in women in the United
States. Over 22,000 cases are diagnosed annually, and there are an
estimated 15,500 deaths per year. The majority of patients have
widespread disease at presentation. The five-year survival for the
advanced-stage disease remains less than 30 percent. Combining GPS
with the checkpoint inhibitor pembrolizumab, which beneficially and
profoundly alters the tumor microenvironment (TME), is hypothesized
to increase the proportion of patients who develop an immune
response against their cancer and potentially improve their
clinical outcome over pembrolizumab monotherapy, without the burden
of additional toxicities in macroscopically measurable
malignancies.
About SELLAS Life Sciences Group,
Inc. SELLAS is a late-stage clinical biopharmaceutical
company focused on developing novel cancer immunotherapeutics for a
broad range of indications. SELLAS’ lead product candidate, GPS, is
licensed from Memorial Sloan Kettering Cancer Center and targets
the WT1 protein, which is present in an array of tumor types. GPS
has potential both as a monotherapy and in combination to address a
broad spectrum of hematologic malignancies and solid tumor
indications. SELLAS’ second product candidate, nelipepimut-S (NPS),
is a HER2-directed cancer immunotherapy with potential to treat
patients with early-stage breast cancer with low to intermediate
HER2 expression, otherwise known as HER2 1+ or 2+, which includes
triple negative breast cancer patients, following the standard of
care.
For more information on SELLAS, please
visit www.sellaslifesciences.com.
Keytruda® is a registered trademark of Merck &
Co., Inc., Kenilworth, N.J., USA (known as MSD outside the United
States and Canada), and is not a trademark of SELLAS. The
manufacturer of this brand is not affiliated with and does not
endorse SELLAS or its products.
Forward-Looking Statements This
press release contains forward-looking statements. All statements
other than statements of historical facts are “forward-looking
statements,” including those relating to future events. In some
cases, forward-looking statements can be identified by terminology
such as “plan,” “expect,” “anticipate,” “may,” “might,” “will,”
“should,” “project,” “believe,” “estimate,” “predict,” “potential,”
“intend,” or “continue” and other words or terms of similar
meaning. These statements include, without limitation, statements
related to the clinical development of GPS for ovarian cancer, and
the potential for GPS as a drug development candidate. These
forward-looking statements are based on current plans, objectives,
estimates, expectations, and intentions, and inherently involve
significant risks and uncertainties. Actual results and the timing
of events could differ materially from those anticipated in such
forward-looking statements as a result of these risks and
uncertainties, which include, without limitation, risks and
uncertainties associated with the COVID-19 pandemic and its impact
on the Company’s clinical plans, risks and uncertainties associated
with immune-oncology product development and clinical success
thereof, the uncertainty of regulatory approval, and other risks
and uncertainties affecting SELLAS and its development programs as
set forth under the caption “Risk Factors” in SELLAS’ Annual Report
on Form 10-K filed on March 23, 2021 and in its other SEC filings.
Other risks and uncertainties of which SELLAS is not currently
aware may also affect SELLAS’ forward-looking statements and may
cause actual results and the timing of events to differ materially
from those anticipated. The forward-looking statements herein are
made only as of the date hereof. SELLAS undertakes no obligation to
update or supplement any forward-looking statements to reflect
actual results, new information, future events, changes in its
expectations or other circumstances that exist after the date as of
which the forward-looking statements were made.
Investor Contacts Valter Pinto /
Allison Soss KCSA Strategic Communications Email: SELLAS@kcsa.com
Phone: 914.907.2675 / 215.272.2707
Media Contacts Caitlin Kasunich /
Raquel Cona KCSA Strategic Communications Email: SELLAS@kcsa.com
Phone: 212.896.1241 / 212.896.1276
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