Astellas Pharma already has a piece of the market for antibody drug conjugates (ADCs), a type of cancer therapy that has seen a surge in progress in recent years. The Japanese pharmaceutical giant co-developed Padcev, which has approvals in bladder cancer, under a partnership with U.S. biotech Seagen. Astellas wants to take the targeted approach of ADCs a step further and to do that it’s partnering with another U.S. company. The new alliance with Sutro Biopharma is focused on using that biotech’s technology to develop ADCs with an extra anti-cancer punch.
The agreement calls for Astellas to pay its new partner $90 million up front. The companies aim to develop ADCs addressing three undisclosed biological targets.
An ADC is a type of therapy made by linking a targeting antibody to a cancer-killing drug payload. The targeting capability of the antibody is meant to deliver a precision strike to tumors that spares healthy tissue. South San Francisco-based Sutro has technology that adds a second drug to the ADC molecule. This additional drug stimulates the immune system, eliciting an immune response to the targeted tumor cells. Sutro calls these drugs immunostimulant ADCs, or iADCs.
“Our novel iADC design is intended to deliver two different drugs directly to the tumor, and not only kill tumor cells but also locally prime an immune response to the patient’s particular tumor cells,” the company explained in its 2021 annual report. “We believe that our iADC approach creates a new therapeutic opportunity by combining the best features of an ADC with the biology of a personalized vaccine.”
There’s more to the iADC approach. One of the challenges for all cancer immunotherapies is that tumors have immunosuppressive features that make them “cold,” meaning that the tumors don’t spark a strong immune response. The partners say the iADC technology of Sutro has the potential turn cold tumors into hot ones. In a prepared statement, Sutro CEO William Newell said that iADC research could lead to new treatment options for patients whose cancers do not respond to currently available immunotherapies.
According to deal terms announced late Monday, Sutro could earn up to $422.5 million in milestone payments for each product candidate developed under the partnership. In addition, Sutro would receive royalties from sales if any of these iADCs reach the market. This agreement could play out in a similar way to the deal covering the development of Padcev, which is co-commercialized in the U.S. by Astellas and Seagen. Sutro has the option to share with Astellas in the development costs of a drug candidate in the U.S. If the biotech exercises this option, the U.S. development costs and profits (or losses) from a commercialized therapy will be split equally. The agreement does not prevent Sutro from developing additional iADCs for other targets outside of the Astellas partnership.
Astellas is the latest pharma partner to sign on with Sutro. An ADC for multiple myeloma has reached early clinical development under a partnership with Bristol Myers Squibb. An alliance with EMD Serono is focused on a bispecific ADC for non-small cell lung cancer and esophageal cancer. Sutro’s most advanced internal program, STRO-002, has reached early clinical testing in ovarian cancer among other types of solid tumors.
The field of ADC drug research has led to dealmaking and drug approvals. So far, the ADC drug class has about a dozen FDA-approved therapies from companies that include Seagen, Roche, ADC Therapeutics, and Gilead Sciences. Drugmakers are also finding opportunities to expand use of approved products to more patients. For example, at the annual meeting of the American Society of Clinical Oncology earlier this month, AstraZeneca presented data showing how its approved drug Enhertu can reach a group of breast cancer patients previously thought to out of reach for this type of targeted therapy. One of the problems with ADCs is that some of the drug payload is released before the drug reaches its destination, leading to off-target effects. ADC startups such as Mythic Therapeutics are developing technologies intended to ensure that more of the toxic drug goes to tumors and not healthy cells.