Localized CD47 blockade enhances immunotherapy for murine melanoma

Area of Science:

• Immunology
• Oncology
• Biotechnology

Background:

• CD47 is an antiphagocytic ligand on normal and malignant cells, inhibiting immune responses via SIRPα.
• CD47 inhibitors enhance anti-tumor antibody responses by promoting phagocytosis in models.
• Widespread CD47 expression, especially on erythrocytes, acts as an antigen sink, potentially limiting therapy efficacy.

Purpose of the Study:

• To develop a nanobody (A4) targeting the CD47-SIRPα interaction.
• To evaluate A4's efficacy alone and in combination with immunotherapies in a syngeneic melanoma model.
• To investigate strategies for overcoming CD47-related challenges in cancer immunotherapy.

Main Methods:

• Generation of a nanobody (A4) that blocks CD47-SIRPα interaction.
• Assessment of A4 in combination with anti-PD-L1 and anti-CTLA4 therapies in B16F10 melanoma models.
• Development of a B16F10 cell line secreting A4 to achieve localized CD47 blockade.

Main Results:

• A4 synergized with anti-PD-L1 but not anti-CTLA4 therapy.
• Increased dosing or Fc-fusion of A4 did not overcome the antigen sink issue or systemic toxicity.
• Localized CD47 blockade via A4 secretion from tumor cells enhanced immune responses.

Conclusions:

• Near-complete CD47 blockade within the tumor microenvironment is crucial for enhancing immune therapies.
• Strategies focusing on localized CD47 blockade may overcome limitations of systemic approaches.
• Targeting the CD47-SIRPα axis holds promise for improving cancer immunotherapy outcomes.