Candidate: Ligand Antigen Epitope Presentation System (LEAPS) COVID 19 peptide conjugates

Type: Immunotherapy based on CEL-SCI’s patented LEAPS peptide platform technology, directed towards antigens within the NP protein of COVID-19 that elicit cytolytic T cell responses. Such responses attack the virus infected cellular “factories” within the infected host in order to eliminate the source of virus and help subdue the infection, CEL-SCI reasons. LEAPS peptides use conserved regions of coronavirus proteins to stimulate protective cell mediated T cell responses and reduce viral load.

Status: CEL-SCI said July 24 it concluded animal experiments using its LEAPS COVID 19 peptide conjugates, with the data supportive of advancing into animal challenge studies with live virus SARS-CoV-2 at the University of Georgia Vaccine Center.

The animal experiments showed that after only one injection, LEAPS COVID 19 conjugates induced faster and much higher than expected antibody responses against a non-mutating region of SARS-CoV-2. IgG antibodies response was generated within 10 days of a single immunization, CEL-SCI said.

“We now have the immunogenicity data showing that the LEAPS technology may work against COVID 19,” Daniel Zimmerman, PhD, CEL-SCI Senior VP of Research Cellular Immunology, said in a statement.

In March, CEL-SCI said it signed a collaboration agreement with the University of Georgia’s Center for Vaccines and Immunology to develop a LEAPS COVID-19 immunotherapy designed to treat patients at highest risk of dying from COVID-19. The collaboration will commence with pre-clinical studies based on the experiments previously conducted with LEAPS immunotherapy in collaboration with the National Institutes for Allergies and Infectious Diseases (NIAID) against another respiratory virus, H1N1, involved in the 2009 H1N1 flu pandemic.

The proposed LEAPS peptides for the COVID-19 study are directed towards antigens within the NP protein of SARS-Cov-2 virus that elicit cytolytic T cell responses. Unlike the viral glycoprotein “spike” antigens which are important for antibody-based vaccines, these NP-antigens are less variable between viral strains and less likely to change in response to antibodies elicited by prior infection or other vaccines, according to CEL-SCI. Cytolytic T cell responses attack the virus infected cellular “factories” within the infected host in order to eliminate the source of virus and help subdue the infection.

Also in March, CEL-SCI said it will develop an immunotherapy to treat COVID-19 and other diseases for which disease associated antigenic peptide(s) sequences have already been identified—including several other infectious diseases, some types of cancer, allergic asthma and allergy, select CNS diseases such as Alzheimer’s, and autoimmune diseases such as rheumatoid arthritis.

According to CEL-SCI, LEAPS has shown in several animal models the ability to design antigen-specific immunotherapeutic peptides that preferentially direct the immune response to a cellular, humoral (antibody) or mixed response and are also capable of enhancing important T-regulatory (Treg) responses. CEL-SCI has been awarded a $1.5 million grant by the NIH’s National Institute of Arthritis and Musculoskeletal and Skin Diseases toward IND-enabling studies of a LEAPS-based treatment in arthritis.

COVID-19: 200 Candidates and Counting

To navigate through the >200 potential therapeutic and vaccine options for COVID-19, GEN has grouped the candidates into four broad categories based on their developmental and (where applicable) clinical progress:

FRONT RUNNER – the most promising therapeutics/vaccines based on clinical progress, favorable data or both.

DEFINITELY MAYBE – earlier phases with promising partners, or more advanced candidates in development that have generated uneven data

KEEPING AN EYE ON… – interesting technology, attracting notable partners, or both, but preliminary data.

TOO SOON TO TELL – longshots pending additional experimental and/or clinical data.

GEN has also tagged the most common treatment types:


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