IAP antagonists induce anti-tumor immunity in multiple myeloma

Area of Science:

• Oncology
• Immunology
• Pharmacology

Background:

• Cellular inhibitors of apoptosis (cIAP) 1 and 2 are implicated in cancer's evasion of apoptosis and are therapeutic targets.
• Small-molecule IAP antagonists, such as LCL161, are being investigated for cancer therapy.
• cIAP1 and cIAP2 deletions in multiple myeloma (MM) activate the NF-κB pathway.

Purpose of the Study:

• To investigate the efficacy of LCL161 in a multiple myeloma mouse model and in patients.
• To elucidate the mechanism of LCL161's anti-myeloma activity.

Main Methods:

• In vivo studies using a transgenic myeloma mouse model.
• Clinical evaluation in patients with relapsed-refractory MM.
• Analysis of immune signaling pathways and cellular responses.

Main Results:

• LCL161 demonstrated robust in vivo anti-myeloma activity, with a median progression-free survival of 10 months when combined with cyclophosphamide in patients.
• The anti-myeloma effect was mediated by type I interferon signaling and inflammatory responses, leading to macrophage and dendritic cell activation and tumor cell phagocytosis.
• LCL161 induced long-term anti-tumor protection and regression in a fraction of mice, with curative potential when combined with anti-PD1.

Conclusions:

• LCL161 exhibits significant anti-myeloma activity through immune modulation rather than direct tumor cell apoptosis.
• Combination therapy with LCL161, cyclophosphamide, and anti-PD1 shows curative potential in preclinical models.
• Targeting cIAP1/2 with antagonists like LCL161 represents a promising strategy for MM treatment.