DNA-PK Inhibitor Peposertib Amplifies Radiation-Induced Inflammatory Micronucleation and Enhances TGFβ/PD-L1 Targeted Cancer Immunotherapy

Abstract

Radiation therapy is the most widely used cancer treatment and improvements in its efficacy and safety are highly sought-after. Peposertib (also known as M3814), a potent and selective DNA-PK inhibitor, effectively suppresses the repair of radiation-induced DNA double-strand breaks (DSB) and regresses human xenograft tumors in preclinical models. Irradiated cancer cells devoid of p53 activity are especially sensitive to the DNA-PK inhibitor, as they lose a key cell cycle checkpoint circuit and enter mitosis with unrepaired DSBs, leading to catastrophic consequences. Here, we show that inhibiting the repair of DSBs induced by ionizing radiation with peposertib offers a powerful new way for improving radiotherapy by simultaneously enhancing cancer cell killing and response to a bifunctional TGFβ "trap"/anti-PD-L1 cancer immunotherapy. By promoting chromosome misalignment and mis-segregation in p53-deficient cancer cells with unrepaired DSBs, DNA-PK inhibitor accelerated micronuclei formation, a key generator of cytosolic DNA and activator of cGAS/STING dependent inflammatory signaling as it elevated PD-L1 expression in irradiated cancer cells. Triple combination of radiation, peposertib and bintrafusp alfa, a fusion protein simultaneously inhibiting the pro-fibrotic TGFβ and immunosuppressive PD-L1 pathways was superior to dual combinations and suggested a novel approach to more efficacious radioimmunotherapy of cancer. IMPLICATIONS Selective inhibition of DNA-PK in irradiated cancer cells enhances inflammatory signaling and activity of dual TGFβ/PD-L1 targeted therapy and may offer a more efficacious combination option for the treatment of locally advanced solid tumors.

Anti-cancer immune responses to DNA damage response inhibitors: Molecular mechanisms and progress toward clinical translation

“…Due to the dependence of AZD7648 on type I IFN responses, it would be interesting to combine this drug with immunomodulatory drugs that enhance the type I IFN response. Additionally, the DNA-PKi peposertib enhanced RT-induced TGFβ/PD-L1-targeted immunotherapy in mice, further supporting the combination of DNA-PKi, RT, and immunotherapy ( 69 ).…”

“…Further, studies have shown that DNA damage-induced upregulation of PD-L1 by cisplatin or ionizing radiation was suppressed by co-administration with ATRi agents ( 67 ). DNA-PK inhibitors seem to upregulate PD-L1 ( 69 ) along with WEE1 inhibitors ( 2 ) and Chk1/2 inhibitors ( 70 , 71 ), likely by preventing the repair of double-stranded DNA breaks, which activates STAT1/3 signaling through ATM/ATR/Chk1 kinases, resulting in an upregulation of PD-L1 levels ( 60 ).…”

Selective ATM inhibition augments radiation-induced inflammatory signaling and cancer cell death

“…50 metaphase spreads per treatment were scored for chromosomal aberrations. For spectral karyotyping (SKY) analysis, fixed cells were processed as described elsewhere [ 32 ]. Ten metaphase spreads were analyzed per treatment condition.…”

Treatment Considerations for Patients with Locoregionally Advanced Head and Neck Cancer with a Contraindication to Cisplatin

“…An ongoing phase I trial (NRG-HN008), is evaluating the use of peposertib, a DNA-dependent protein kinase RT, radiation therapy; LRC, locoregional control; LRF, locoregional failure; PFS, progression-free survival; OS, overall survival; AE, adverse events (DNA-PK) inhibitor, with RT in LA-HNC patients with a contraindication to cisplatin [68]. Preclinical have demonstrated that this agent suppresses repair of radiation-induced DNA double-strand breaks, increases PD-L1 expression on cancer cells, and enhances inflammatory signaling [69]. Another class of agents includes second mitochondria-derived activator of caspases (SMAC) mimetics, which antagonize apoptosis inhibitor proteins (IAPs) and exhibit radiosensitizing effects via caspase-dependent and CD8 T cell-dependent pathways [70••].…”