Durable antitumor responses to CD47 blockade require adaptive immune stimulation.

Area of Science:

• Immunology
• Cancer Biology
• Pharmacology

Background:

• Therapeutic antitumor antibodies leverage innate and adaptive immunity against cancer.
• Tumor cells use the CD47-signal regulatory protein alpha (SIRPα) axis to evade immune responses.
• CD47 blockade enhances antibody-dependent cellular phagocytosis (ADCP) in xenografts, but its efficacy in immunocompetent hosts is unclear.

Purpose of the Study:

• To investigate the efficacy of CD47 blockade as an adjuvant therapy for antitumor antibodies in immunocompetent hosts.
• To determine the role of innate and adaptive immunity in response to CD47-targeted therapies.
• To identify optimal combination strategies for potentiating antitumor antibody efficacy.

Main Methods:

• Utilized syngeneic B16F10 tumor models in mice.
• Administered CD47 blockade, tumor-specific monoclonal antibodies, and programmed death-ligand 1 (PD-L1) blockade in various combinations.
• Assessed tumor growth, immune cell infiltration, and development of durable antitumor immunity.

Main Results:

• CD47 blockade alone or with antitumor antibodies did not induce significant antitumor immunity in syngeneic mouse models.
• Combination therapy involving PD-L1 blockade and an antitumor antibody was required for durable tumor immunity.
• Incorporating CD47 antagonism into the PD-L1 blockade and antitumor antibody combination substantially improved response rates.

Conclusions:

• The adaptive immune system plays a critical, underappreciated role in the efficacy of anti-CD47 adjuvant therapy.
• Targeting both innate (CD47) and adaptive (PD-L1) immune checkpoints is crucial for potentiating antitumor antibody therapy.
• Combination immunotherapies that engage both innate and adaptive immunity hold promise for enhancing cancer treatment outcomes.