Image Credit: Christine Daniloff, (MIT, stock images)

Vaccinating Against Certain Proteins Found on Cancer Cells Could Help Enhance the T Cell Response to Tumors

Anne Trafton | 
MIT News Office

Over the past decade, scientists have been exploring vaccination as a way to help fight cancer. These experimental cancer vaccines are designed to stimulate the body’s own immune system to destroy a tumor, by injecting fragments of cancer proteins found on the tumor.

So far, none of these vaccines have been approved by the FDA, but some have shown promise in clinical trials to treat melanoma and some types of lung cancer. In a new finding that may help researchers decide what proteins to include in cancer vaccines, MIT researchers have found that vaccinating against certain cancer proteins can boost the overall T cell response and help to shrink tumors in mice.

The research team found that vaccinating against the types of proteins they identified can help to reawaken dormant T cell populations that target those proteins, strengthening the overall immune response.

“This study highlights the importance of exploring the details of immune responses against cancer deeply. We can now see that not all anticancer immune responses are created equal, and that vaccination can unleash a potent response against a target that was otherwise effectively ignored,” says Tyler Jacks, the David H. Koch Professor of Biology, a member of the Koch Institute for Integrative Cancer Research, and the senior author of the study.

MIT postdoc Megan Burger is the lead author of the new study, which appears today in Cell.

T Cell Competition

When cells begin to turn cancerous, they start producing mutated proteins not seen in healthy cells. These cancerous proteins, also called neoantigens, can alert the body’s immune system that something has gone wrong, and T cells that recognize those neoantigens start destroying the cancerous cells.

Eventually, these T cells experience a phenomenon known as “T cell exhaustion,” which occurs when the tumor creates an immunosuppressive environment that disables the T cells, allowing the tumor to grow unchecked.

Scientists hope that cancer vaccines could help to rejuvenate those T cells and help them to attack tumors. In recent years, they have worked to develop methods for identifying neoantigens in patient tumors to incorporate into personalized cancer vaccines. Some of these vaccines have shown promise in clinical trials to treat melanoma and non-small cell lung cancer.

“These therapies work amazingly in a subset of patients, but the vast majority still don’t respond very well,” Burger says. “A lot of the research in our lab is aimed at trying to understand why that is and what we can do therapeutically to get more of those patients responding.”

Previous studies have shown that of the hundreds of neoantigens found in most tumors, only a small number generate a T cell response.

The new MIT study helps to shed light on why that is. In studies of mice with lung tumors, the researchers found that as tumor-targeting T cells arise, subsets of T cells that target different cancerous proteins compete with each other, eventually leading to the emergence of one dominant population of T cells. After these T cells become exhausted, they still remain in the environment and suppress any competing T cell populations that target different proteins found on the tumor.

However, Burger found that if she vaccinated these mice with one of the neoantigens targeted by the suppressed T cells, she could rejuvenate those T cell populations.

“If you vaccinate against antigens that have suppressed responses, you can unleash those T cell responses,” she says. “Trying to identify these suppressed responses and specifically targeting them might improve patient responses to vaccine therapies.”

Shrinking Tumors

In this study, the researchers found that they had the most success when vaccinating with neoantigens that bind weakly to immune cells that are responsible for presenting the antigen to T cells. When they used one of those neoantigens to vaccinate mice with lung tumors, they found the tumors shrank by an average of 27 percent.

“The T cells proliferate more, they target the tumors better, and we see an overall decrease in lung tumor burden in our mouse model as a result of the therapy,” Burger says.

After vaccination, the T cell population included a type of cells that have the potential to continuously refuel the response, which could allow for long-term control of a tumor.

In future work, the researchers hope to test therapeutic approaches that would combine this vaccination strategy with cancer drugs called checkpoint inhibitors, which can take the brakes off exhausted T cells, stimulating them to attack tumors. Supporting that approach, the results published today also indicate that vaccination boosts the number of a specific type of T cells that have been shown to respond well to checkpoint therapies.

The research was funded by the Howard Hughes Medical Institute,
the Ludwig Center at Harvard University, the National Institutes of Health, the
Koch Institute Support (core) Grant from the National Cancer Institute, the
Bridge Project of the Koch Institute and Dana-Farber/Harvard Cancer Center, and
fellowship awards from the Jane Coffin Childs Memorial Fund for Medical
Research and the Ludwig Center for Molecular Oncology at MIT.

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Onconova Therapeutics, Inc. Announces Pricing Of $21 Million Public Offering Of Common Stock

NEWTOWN, Pa., Sept. 24, 2021 (GLOBE NEWSWIRE) — Onconova Therapeutics, Inc. (NASDAQ: ONTX) (“Onconova”), a biopharmaceutical company focused on discovering and developing novel products to treat cancer, today announced the pricing of an underwritten public offering of 5,000,000 shares of its common stock at a public offering price of $4.20 per share. The gross proceeds of the offering to the Company are expected to be $21 million, before deducting the underwriting discounts and commissions and other estimated offering expenses. In addition, Onconova granted the underwriters a thirty-day option to purchase up to an additional 750,000 shares of common stock at the public offering price, less underwriting discounts and commissions.

The closing of the offering is expected to occur on or about September 28, 2021, subject to the satisfaction of customary closing conditions.

Guggenheim Securities is acting as sole book-running manager. Ladenburg Thalmann & Co. Inc. and Noble Capital Markets, Inc. are acting as co-managers for the offering.

The securities described above are being offered by Onconova pursuant to a shelf registration statement on Form S-3 (File No. 333-237844) which was initially filed by the Company with the Securities and Exchange Commission (the “SEC”) on April 24, 2020, amended on Form S-3/A that was filed with the SEC on May 15, 2020, and was declared effective by the SEC on May 18, 2020.

A preliminary prospectus supplement relating to the offering was filed with the SEC on September 23, 2021 and is available on the SEC’s website at http://www.sec.gov. The final prospectus supplement relating to and describing the terms of the offering will be filed with the SEC and also will be available on the SEC’s website. Before investing in the offering, you should read each of the prospectus supplement and the accompanying prospectus relating to the offering in their entirety as well as the other documents that the Company has filed with the SEC that are incorporated by reference in the prospectus supplement and the accompanying prospectus relating to the offering, which provide more information about the Company and the offering. Copies of the final prospectus supplement, when available, and accompanying prospectus relating to the offering may be obtained from Guggenheim Securities, LLC Attention: Equity Syndicate Department, 330 Madison Avenue, New York, NY 10017 or by telephone at (212) 518-9544, or by email at GSEquityProspectusDelivery@guggenheimpartners.com.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy any of the securities described herein, nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

About Onconova Therapeutics, Inc.

Onconova Therapeutics is a clinical-stage biopharmaceutical company focused on discovering and developing novel products for patients with cancer. The Company has proprietary targeted anti-cancer agents designed to disrupt specific cellular pathways that are important for cancer cell proliferation.

Onconova’s novel, proprietary multi-kinase inhibitor ON 123300 is being evaluated in two separate and complementary Phase 1 dose-escalation and expansion studies. These trials are currently underway in the United States and China.

Onconova’s product candidate rigosertib is being studied in an investigator-initiated study program, including in a dose-escalation and expansion Phase 1/2a investigator-initiated study with oral rigosertib in combination with nivolumab for patients with KRAS+ non-small cell lung cancer.

Forward-Looking Statements

Some of the statements in this release are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, Section 21E of the Securities Exchange Act of 1934, as amended, and the Private Securities Litigation Reform Act of 1995, and involve risks and uncertainties. These statements relate to Onconova’s expectations regarding the offering, its patents and clinical development plans including patient enrollment timelines and indications for its product candidates. Onconova has attempted to identify forward-looking statements by terminology including “believes,” “estimates,” “anticipates,” “expects,” “plans,” “intends,” “may,” “could,” “might,” “will,” “should,” “approximately” or other words that convey uncertainty of future events or outcomes. Although Onconova believes that the expectations reflected in such forward-looking statements are reasonable as of the date made, expectations may prove to have been materially different from the results expressed or implied by such forward-looking statements. These statements are only predictions and involve known and unknown risks, uncertainties, and other factors, including the success and timing of Onconova’s clinical trials and regulatory agency and institutional review board approvals of protocols, Onconova’s ability to continue as a going concern, the need for additional financing, Onconova’s collaborations, market conditions and those discussed under the heading “Risk Factors” in Onconova’s most recent Annual Report on Form 10-K and quarterly reports on Form 10-Q. Any forward-looking statements contained in this release speak only as of its date. Onconova undertakes no obligation to update any forward-looking statements contained in this release to reflect events or circumstances occurring after its date or to reflect the occurrence of unanticipated events.

General Contact

Avi Oler
Onconova Therapeutics, Inc.
267-759-3680
ir@onconova.us
http://www.onconova.com/contact/