Background

Neoadjuvant PD-1 blockade produces major pathological responses (MPR) in ~30% of patients (pts) with high-risk resectable melanoma (MEL) with durable relapse-free benefit, and increased circulating activated CD8+ T cells.^{1 2} CMP-001 is a type A CpG packaged within a virus-like particle that activates tumor-associated plasmacytoid dendritic cells (pDC) via TLR9 inducing type I interferons and anti-tumor CD8+ T cells. CMP-001/pembrolizumab produces durable anti-tumor responses in PD-1 refractory melanoma.³ We previously reported preliminary evidence of efficacy of neoadjuvant IT CMP/Nivo in high-risk resectable MEL; and herein present final results on 30 evaluable patients.

Methods

30 pts with stage III B/C/D MEL were enrolled. Pre-operatively, CMP-001 was dosed at 5 mg subcutaneous (SC, 1st), then 10 mg IT (2nd-7th) weekly; Nivo was dosed 240 mg q2 weeks for 3 doses – both agents given for 7 weeks. Post-operatively, Nivo was dosed 480 mg q4 weeks with CMP-001 5 mg q4 weeks SC for 48 weeks. Primary endpoints included major pathologic response rate (MPR), and incidence of dose-limiting toxicities (DLT). Secondary endpoints were radiographic response, relapse-free survival (RFS) and overall survival (OS). Pathological response was scored blinded by pathologists based on residual volume of tumor (RVT) using prior specified cutoffs:^{4 6}0% (complete response, pCR); 0%<rvt<rvt50% (non-response, pNR). Radiographic response was assessed using RECIST v1.1. Sequential blood draws and tumor biopsies were collected and analyzed for CD8+ T cell infiltrate (TIL), multiparameter flow cytometry (MFC) and multiplex immunofluorescence (mIF).

Results

30 pts with regionally advanced MEL were enrolled, of stages IIIB (57%), IIIC (37%), IIID (7%). 29/30 (97%) of pts completed 7 weeks of neoadjuvant Nivo/CMP; while 1 pt had a delay in surgery related to a pre-operative infection unrelated to therapy. No DLTs were reported; grade 3/4 irAE were reported in 3 pts (11%) leading to CMP-001 discontinuation in 2 pts (7%). Radiographic responses were seen in 13 pts (43%), while 9 pts (30%) had stable disease and 8 pts (27%) had progressive disease. Pathological responses (RVT <50%) were seen in 70% of pts: pCR 15 (50%), pMR 3 (10%), 3 pPR (10%); only 9 (30%) had pNR. Pathological responders (pCR/pMR) had increased CD8+ TIL and CD303+ pDC intra-tumorally by mIF; and peripherally activated PD1+/Ki67+ CD8+ T cells by MFC.

Conclusions

Neoadjuvant CMP/Nivo has acceptable toxicity and promising efficacy. MPR is 60% in 30 pts. 1-year RFS was 82% (all pts) and 89% (among those with pCR/pMR); median RFS is 9 months (among pNR/pPR) and not reached (among pCR/pMR). Response is associated with evidence of immune activation intra-tumorally and peripherally. IT CMP001 increases clinical efficacy of PD-1 blockade with minimal additional toxicity in pts with regionally advanced MEL. Further study of this combination in high-risk resectable MEL is planned.

Acknowledgements

We thank Dr. Jagjit Singh and the pathology grossing room staff for their assistance and Checkmate Pharmaceuticals for funding and CMP-001.

Trial Registration

Clinical trial information: NCT03618641

Ethics Approval

The study was approved by University of Pittsburgh’s Institutional Review Board, approval number MOD19040237-002.

Consent

Written informed consent was obtained from the patient for publication of this abstract and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.

References

Amaria RN, Reddy SM, Tawbi HA, et al. Neoadjuvant immune checkpoint blockade in high-risk resectable melanoma. Nat Med 2018. Nov;24(11):1649–1654. Huang AC, Orlowski RJ, Xu X, et al. A single dose of neoadjuvant PD-1 blockade predicts clinical outcomes in resectable melanoma. Nat Med 2019. Mar;25(3):454–461. doi: 10.1038/s41591-019-0357-y. Milhem M, Gonzales R, Medina T, et al. Abstract CT144: Intratumoral toll-like receptor 9 (TLR9) agonist, CMP-001, in combination with pembrolizumab can reverse resistance to PD-1 inhibition in a phase Ib trial in subjects with advanced melanoma. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14–18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract CT144. Tetzlaff MT, Messina JL, Stein JE, et al. Pathological assessment of resection specimens after neoadjuvant therapy for metastatic melanoma. Ann Oncol 2018. Aug 1;29(8):1861–1868. Cottrell TR, Thompson ED, Forde PM, et al. Pathologic features of response to neoadjuvant anti-PD-1 in resected non-small-cell lung carcinoma: a proposal for quantitative immune-related pathologic response criteria (irPRC). Ann Oncol 2018 Aug 1;29(8):1853–1860. doi: 10.1093/annonc/mdy218. Stein JE, Soni A, Danilova L, et al. Major pathologic response on biopsy (MPRbx) in patients with advanced melanoma treated with anti-PD-1: evidence for an early, on-therapy biomarker of response. Ann Oncol 2019 Apr 1;30(4):589–596. doi: 10.1093/annonc/mdz019.

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