Rubius Therapeutics is dropping its lead drug candidate—and its focus on rare diseases—in favor of earlier-stage cell therapies that it has been developing for oncology and autoimmune disorders.
The Cambridge, MA-based company disclosed the strategy shift Thursday in its report of fourth quarter and full year 2019 financial results. After the announcement, shares of Rubius (NASDAQ: RUBY) plummeted, closing down 39 percent at $3.99 apiece from $6.55 per share Wednesday.
Rubius is developing a new class of cell therapies based on red blood cells, which circulate naturally in the body. The company engineers its cells to express therapeutic proteins as a way to treat disease. Phenylketonuria (PKU), a rare metabolic disorder that does not have an FDA approved treatment, was initially the biotech’s lead disease target.
A Phase 1b trial testing of PKU experimental therapy RTX-134 dosed its first patient in January. But the company said Thursday that the results were uninterpretable, possibly due to the low dose of cells administered and the sensitivity of the test used to detect circulating cells. Rubius said its decision to end the RTX-134 trial and move away from its other rare disease programs was partly due to delays stemming from its contract manufacturer and the anticipated expense of producing chronic, high-dose therapies for such conditions, which are characterized by enzyme deficiencies.
The progress of Rubius’s oncology drug candidates, including its new lead program, RTX-240, also played a role in the decision, the company said. The FDA recently cleared the drug to enter the clinic for tests in patients with solid tumors. The company’s cell therapies are designed to be allogenic, or “off-the-shelf” treatments, medicines that use genetically engineered cells from healthy donors. T-cell therapies for cancer currently on the market are made from a patient’s own cells. (Read more about the company’s use of red blood cells as therapeutics here.)
When Rubius went public in August 2018, it planned to use $42 million of that $241 million haul to bring RTX-134 through a Phase 1/2a clinical trial. At the end of 2019, Rubius reported $283.3 million in cash, equivalents, and investments. With the shuttering of its rare disease programs and other measures, those funds should be enough to carry it into 2022, the company said Thursday.
Around the turn of the year, Rubius added two new executives: Laurence Turka, a transplant immunologist, as chief scientific officer, and oncologist and immunologist Christina Coughlin, as chief medical officer.
By year’s end the company plans to ask the FDA for permission to start human testing of another of its drug candidates, RTX-321, developed for the treatment of HPV-positive cancers. Contract manufacturing won’t play a role in the progression of its red blood cell therapies for cancer: The company says its manufacturing facility in Smithfield, RI, is prepared to produce the supply needed to test RTX-240 in the clinic and, if OK’d to move into human tests, RTX-321.
The company also plans to focus on advancing its preclinical pipeline of autoimmune treatments, which are engineered to express specific autoimmune disease-associated antigens, either within the cell or on the cell surface, in a bid to retrain the immune system to no longer view these self-antigens as foreign. The company is working on therapies for T cell-mediated autoimmune diseases, including type 1 diabetes.