Targeting the IL-2 inducible kinase in melanoma; a phase 2 study of ibrutinib in systemic treatment-refractory distant metastatic cutaneous melanoma: preclinical rationale, biology, and clinical activity (NCI9922)

Abstract

Background: IL-2 inducible kinase (ITK) is highly expressed in metastatic melanomas and its inhibition suppresses melanoma cell proliferation. We hypothesize that ibrutinib has a direct antitumor effect in melanoma cell lines and that treatment of metastatic melanomas with ibrutinib induces antitumor responses.

Methods: We assessed the ibrutinib effect on melanoma cell proliferation, apoptosis, and motility. Patients with metastatic melanoma refractory to PD-1 and MAPK inhibitors (if BRAFV600-mutant) were treated with ibrutinib, 840 mg PO QD, as part of a phase II clinical trial (clinicaltrials.gov NCT02581930).

Results: Melanoma cell lines frequently express ITK, YES1, and EGFR. Ibrutinib suppressed cell motility and proliferation in most cell lines. Eighteen patients (13 male; median age 63.5 years, range 37-82; 12 with ipilimumab resistance) were enrolled. The most frequent side effects were fatigue (61%), anorexia (50%), hyponatremia (28%), nausea, and vomiting (22% each). No antitumor responses were seen. At a median follow-up of 6 months (0.3-35.8 months), the median progression-free survival was 1.3 months (range 0.2-5.5 months). Fifteen patients were discontinued from the study due to progression, and 14 patients had died from metastatic melanoma. All archived tumors expressed ITK, 41% had no expression of p16 and PTEN, and 61% had absent tumor-infiltrating lymphocytes (TILs). Ibrutinib significantly suppressed proliferating (Ki67+) CD19+ peripheral blood mononuclear cells and had no significant effect on other lymphocyte subsets.

Conclusion: Ibrutinib did not induce any meaningful clinical benefit. ITK expression may not be clinically relevant. Treatment-refractory metastatic melanomas have other fundamental defects (i.e. absent PTEN and p16 expression, absent TILs) that may contribute to an adverse prognosis.

Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.

Figures

Fig. 1.. In vitro effect of ibrutinib on melanoma cell proliferation (A), apoptosis (B), and single-cell motility (C).

See methods for details. Abbreviations. Low, mean Hscore expression

Fig. 2.. Swimmer’s plots of the 18 patients who were enrolled and treated with ibrutinib in the first stage of the NCI9922 trial.

Fig. 3.. Expression of ITK protein in baseline archived/fresh melanoma tissues from the NCI9922 patients.

All but one subject (100) had sufficient tumor for IHC and IF analysis. A. Average fluorescence intensity (counts above background) of ITK in melanoma (Sox10+) cells. Digital images corresponding to melanoma tissues from two different patients who participated in the NCI9922 study (shown with X in A) and express high (B) or low ITK (C) are shown. Sox10 signal is pseudocolored with green and ITK signal is pseudocolored with red.

Fig. 4.. Density of TILs in baseline archived/fresh melanoma tissue from the NCI9922 patients.

A. Density of TILs was quantified in hematoxylin and eosin (H&E)-stained sections as well as in a single-color IHC assay using antibodies against CD8 and CD19 as absent (A), non-brisk (NB), and brisk (B). All but one subject (100) had sufficient tumor for IHC analysis (N/A, not available). B. Digital images corresponding to tissue sections that were stained with an antibody against CD8 and CD19. Examples of absent, non-brisk, and brisk density is shown (cases highlighted in red in A). Please note that only tumor-associated (brown arrows) are considered; lymphocytes that are part of the normal (non-invaded) remaining lymph nodes (yellow arrows) are not considered. C. OS analysis of patients whose baseline tumors have present TILs (non-brisk plus brisk) versus absent lymphocytes are shown.