SELLAS Offers Strong Quarterly Update; Trials and Balance Sheet Support Potential Near-Term Catalysts

SELLAS Life Sciences (NASDAQ: SLS) shares are in focus after the company published its business update and Q2 2020 financial results on Thursday, August 13th. The release reveals a balance sheet as of August 2020 that is strengthened by a completed at-the-market private placement, which raised $9.2 million. The Company also announced that its clinical programs for galinpepimut-S, including its phase 3 REGAL study, is on track, with multiple data readouts expected over the next 18 months.

SELLAS is a late-stage clinical biopharmaceutical company focused on the development of novel cancer immunotherapies for a broad range of cancer indications. The company’s lead program is evaluating galinpepimut-S (GPS) in treating patients with acute myeloid leukemia (AML) who have achieved complete remission after second line anti-leukemic therapy.

Two other studies are also advancing through clinical evaluations. Those include a Phase I/II basket study of GPS in combination with Merck’s (NYSE: MRK) KEYTRUDA and a phase 1 investigator-sponsored clinical trial of GPS in combination with Bristol-Myers Squibb’s anti-PD-1 therapy, nivolumab (Opdivo®), in patients with malignant pleural mesothelioma. Each of these trials are on track to report interim data despite the uncertainty caused by the COVID-19 pandemic.

Path Of GPS To Treat Cancer

SELLAS is focused on developing innovative therapeutic vaccines for cancer, also called onco-vaccines, to advance a class of agents that work directly in the immune system to boost the body’s natural defenses against cancer.

Its flagship product, galinpepimut-S (GPS), is a peptide-based immunotherapeutic with highly sophisticated and broadly differentiating features. It targets the Wilms Tumor-1 (WT1) protein, a well-validated cancer antigen, which was independently prioritized by the National Cancer Institute (NCI) as the #1 target antigen for immunotherapy development

WT1 is found to be present in around 20 cancers, both in solid tumors and hematologic malignanciesand it is densely expressed and subsequently processed within cancer cells, with its various peptide fragments then ‘presented’ on the surface of the cancer cells. Thus, if a patient’s immune system becomes specifically activated against select WT1 peptides, through GPS vaccination, the peptide fragments on the cancer cells can then be recognized by the immune system, and eventually killed by the patient’s T-lymphocytes. Attacking WT1-positive cancers through the above immunologic mechanism could be potentially quite effective, as WT1 does not down-regulate or become mutated frequently, and is also expressed on cancer stem cells (in addition to the replicating cells, which represent the majority of malignant cells within a given tumor).

GPS was discovered at Memorial Sloan Kettering (MSK) and is a unique mixture of four small peptides that are by design chosen to be the most immunogenic fragments of the WT1 protein, two of which are modified amino-acid sequences that induce a strong innate immune response against the WT1 antigen and mitigate against tolerance; this is called the heteroclitic effect. To our knowledge, GPS is the first-ever cancer peptide vaccine using heteroclitic technology.

At MSK, GPS underwent extensive preclinical testing, including validation assays for antigenicity and immunogenicity. Additionally, it validated the ability to induce T-lymphocytes that could lyse (kill) WT1-expressing cancer cells ex vivo (i.e., antigen-specific cytotoxicity).

Importantly, GPS is stable, off-the shelf, does not involve cells (like cell-based vaccines, with their associated complex and expensive manufacturing and distribution attributes), and is open to practically all HLA types. And by design, GPS exhibits a unique ability to both mitigate against immune tolerance, plus induce and activate both CD8+ cytotoxic T-lymphocytes (which are responsible for tumor cell kill) and CD4+ T-cells (a fraction of T-cells that is responsible for establishing long-term immunologic memory.

These benefits are crucial to keep tumor growth in check. It’s also significant that GPS is WT1-specific and is not marred by severe or serious toxicities such as development of cytokine-release syndrome (like CAR-T, TIL and some TCR-T and NK cell approaches) or induction of autoimmunity (seen often with checkpoint inhibitors). 

Ongoing Trials Set Up For Potential Milestones

The company’s pivotal, registration-enabling Phase III trial sets up 2020 to deliver some potential catalysts. Investors need to keep in mind that SELLAS has successfully completed a Phase I and Phase II program using GPS monotherapy in AML in patients who have achieved a status of complete remission.

The company has also seen positive responses using GPS in a very advanced patient population, who initially were diagnosed with AML, received appropriate frontline therapy, but relapsed. When used in the setting of maintenance after achievement of patients’ first complete remission (CR1) following successful front-line antileukemic therapy, GPS demonstrated a median overall survival (OS; since initial AML diagnosis) of 67.6 months across all ages (historical controls: ~24-26 months) and 35.3 months in patients >60 years of age (historical controls: ~12-14.5 months).

In the setting of maintenance after achievement of patients’ second complete remission (CR2) following successful second-line (salvage) antileukemic therapy, i.e., in a much more advanced and older population of AML patients vs. the CR1 setting, a pilot comparative study of GPS demonstrated a median OS (since time of achievement of CR2 status) of 21 months vs. 5.4 months in a contemporaneously treated unvaccinated patient cohort.

The ‘control’ patients had a much shorter median overall survival of just 5.4 months, which is typical of the natural history of AML at that advanced stage. That difference in favor of GPS is highly statistically significant and clinically meaningful. In those studies, SELLAS pointed out that the clinical effect was accompanied by induction of antigen (WT1)-specific potent and prolonged immune responses. 

These positive findings pushed the company to design the currently ongoing randomized pivotal, potentially registration-enabling Phase III trial of GPS in AML CR2 patients, named the REGAL study. The clinical program is the most advanced AML peptide vaccine program in AML globally to-date, and the company estimates that they are at least around four years ahead of even the ‘closest’ competitor in the ‘space’.

The combined opportunities have created an exciting period of transition as a company. Momentum can be carried by the Phase III design and treatment regimen being truly optimized, to maximize the probability of eventual clinical success.

As SELLAS enters the back-end of 2020, investors should stay focused on the company’s evolution, because if GPS is proven effective, it would be the only and first-in-class successful immunotherapy in AML (other than allotransplant). It could also be a first therapy associated with significant differentiative advantages over potential competitors. With interim data likely presented along the way, the first set of interpretable results are expected during the second half of 2021.

Finally, it’s important to note that SELLAS is continuing business development and licensing activities. Opportunities may also present themselves for partnerships stemming from important company assets. In the meantime staying focused on the developments from its lead asset, GPS, may help to deliver rewards as data makes its way to the markets. 


Read the full interview with SELLAS CEO Dr Angelos Stergiou HERE



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