Calidi Biotherapeutics Collaborates with SIGA Technologies to Advance Calidi’s Revolutionary RTNova Virotherapy for Lung Cancer and Metastatic Solid Tumors

  • Calidi’s best-in-class, novel systemic targeted virotherapy program (RTNova) aims to provide a feasible solution to target disseminated tumors with a systemic administration -- a long-pursued breakthrough by the biopharma industry.
  • RTNova utilizes a potent vaccinia virus enveloped by a human cell membrane, designed to evade human immunity and enhance its therapeutic functions.
  • RTNova’s novel therapeutic approach allows for ease of administration and the ability to reach a broad patient population.
  • SIGA will supply TPOXX® (Tecovirimat), an effective antiviral agent against vaccinia virus, to support the development of RTNova and accelerate development of extracellular enveloped vaccinia virus-based anticancer therapies.

Calidi Biotherapeutics, Inc. (NYSE American: CLDI or “Calidi”), a clinical-stage biotechnology company developing a new generation of targeted antitumor virotherapies, today announced that it entered into a collaboration agreement with SIGA Technologies (Nasdaq: SIGA) in the first quarter of 2024, to support the development of Calidi’s systemic and targeted RTNova (CLD-400) virotherapy platform, which has the potential to provide a universal treatment for all tumor types. Calidi will initially focus on developing the RTNova platform for lung cancer and metastatic (or advanced stage) solid tumors which account for the majority of cancer deaths.

The long-term collaboration between Calidi and SIGA aims to harness the capabilities of SIGA’s TPOXX, an antiviral agent effective against vaccinia virus. The initial focus for the collaboration will be on testing the capacity of TPOXX to become a safety switch to manage RTNova’s spread in vivo.

“We believe RTNova is a major breakthrough, and Calidi’s novel systemic targeted virotherapy has the potential to radically shift the treatment landscape for patients across all tumor types,” said Antonio F. Santidrian, Chief Scientific Officer of Calidi Biotherapeutics. “By partnering with SIGA, we will have access to a safety switch during the development process, which could provide assurance to patients, physicians, and regulatory bodies during future clinical trials. We are excited about the possibilities this collaboration brings.”

RTNova, an enveloped vaccinia virus, is designed to survive in the bloodstream, target multiple tumor sites, and kill tumor cells while altering the tumor immune microenvironment. This novel therapeutic approach not only facilitates easier administration but also broadens the potential patient population who can benefit from this treatment

The U.S. Food and Drug Administration (FDA) approved oral TPOXX in July 2018 for the treatment of smallpox to mitigate the impact of a potential outbreak or bioterror attack. Preclinical studies have demonstrated TPOXX’s efficacy against all orthopoxviruses that have been tested, including vaccinia (published in The New England Journal of Medicine, July 2018). The unique mechanism of action of TPOXX coupled with published efficacy in animal studies make it an important addition to the development of vaccinia-based cancer therapies.

About Calidi Biotherapeutics

Calidi Biotherapeutics (NYSE American: CLDI) is a clinical-stage immuno-oncology company with proprietary technology designed to arm the immune system to fight cancer. Calidi’s novel stem cell-based platforms are utilizing potent allogeneic stem cells capable of carrying payloads of oncolytic viruses for use in multiple oncology indications, including high-grade gliomas and solid tumors. Calidi’s clinical stage off-the-shelf, universal cell-based delivery platforms are designed to protect, amplify, and potentiate oncolytic viruses leading to enhanced efficacy and improved patient safety. Calidi’s preclinical off-the-shelf enveloped virotherapies are designed to target disseminated solid tumors. This dual approach can potentially treat, or even prevent, metastatic disease. Calidi Biotherapeutics is headquartered in San Diego, California. For more information, please visit .

About SIGA Technologies and TPOXX®

SIGA Technologies, Inc. is a commercial-stage pharmaceutical company focused on the health security market. Health security comprises countermeasures for biological, chemical, radiological and nuclear attacks (biodefense market), vaccines and therapies for emerging infectious diseases, and health preparedness. Our lead product is TPOXX®, also known as tecovirimat and ST-246®, an orally administered and IV formulation antiviral drug for the treatment of human smallpox disease caused by variola virus. TPOXX is a novel small-molecule drug and the US maintains a supply of TPOXX under Project BioShield. The oral formulation of TPOXX was approved by the FDA for the treatment of smallpox in 2018, and the IV formulation was approved for the same indication in 2022. The full label is available by clicking here. Oral tecovirimat received approval from the European Medicines Agency (EMA) and the Medicines and Healthcare Products Regulatory Agency (MHRA) in the United Kingdom in 2022. The EMA and UK approvals include labeling for oral tecovirimat indicating its use for the treatment of smallpox, monkeypox, cowpox, and vaccinia complications following vaccination against smallpox. The full label is available by clicking here. In September 2018, SIGA signed a contract with the Biomedical Advanced Research and Development Authority (BARDA), part of the office of the Administration for Strategic Preparedness and Response within the U.S. Department of Health and Human Services, for additional procurement and development related to both oral and intravenous formulations of TPOXX. For more information about SIGA, please visit

Forward-Looking Statements

This press release may contain forward-looking statements for purposes of the “safe harbor” provisions under the United States Private Securities Litigation Reform Act of 1995. Terms such as “anticipates,” “believe,” “continue,” “could,” “estimate,” “expect,” “intends,” “may,” “might,” “plan,” “possible,” “potential,” “predicts,” “project,” “should,” “towards,” “would” as well as similar terms, are forward-looking in nature, but the absence of these words does not mean that a statement is not forward-looking. These forward-looking statements include, but are not limited to, statements concerning upcoming key milestones (including the reporting of interim clinical results and the dosing of patients), planned clinical trials, and statements relating to the safety and efficacy of Calidi’s therapeutic candidates in development. Any forward-looking statements contained in this discussion are based on Calidi’s current expectations and beliefs concerning future developments and their potential effects and are subject to multiple risks and uncertainties that could cause actual results to differ materially and adversely from those set forth or implied in such forward-looking statements. These risks and uncertainties include, but are not limited to, the risk that Calidi is not able to raise sufficient capital to support its current and anticipated clinical trials, the risk that early results of clinical trials do not necessarily predict final results and that one or more of the clinical outcomes may materially change following more comprehensive review of the data, and as more patient data becomes available, the risk that Calidi may not receive FDA approval for some or all of its therapeutic candidates. Other risks and uncertainties are set forth in the section entitled “Risk Factors” and “Cautionary Note Regarding Forward-Looking Statements” in the Company’s Registration Statements filed with the SEC on Form S-4 filed on August 2, 2023, on Form S-1 filed on October 6, 2023, on Form S-1 filed on January 29, 2024, as amended on February 7, 2024, on Form 10-K filed on March 15, 2024, and Final Prospectus filed on April 17, 2024.


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