A pilot study of interferon-alpha-2b dose reduction in the adjuvant therapy of high-risk melanoma

Abstract

Melanoma is a highly immunogenic tumor and consequently, efforts have been centered on the development of immune-based treatments for this malignancy [1]. Interferons were initially described in the mid-1950s as proteins that interfere with viral replication [2, 3]. Interferons are cytokines that activate Janus kinases (Jak), which lead to phosphorylation and activation of transcription factors belonging to the signal transducer and activator of transcription (STAT) family [4, 5]. Interferon-alpha (IFN-α) became available for use in clinical trials in the mid-1980s [6]. Results suggested that IFN-α inhibited the proliferation of malignant cells and stimulated immune effectors; therefore, IFN-α was initially used in patients with advanced disease [7, 8]. Since then, several meta-analyses have demonstrated that high-dose adjuvant IFN-α (daily 20 MU/m2 intravenous induction therapy for 1 month followed by maintenance subcutaneous 10 MU/m2 three times per week for at least 1 year) can prolong the disease-free interval in high-risk melanoma patients [9]. The introduction of checkpoint inhibitor therapy has revolutionized the adjuvant therapy of melanoma; however, there remains a role for IFN-α in this setting based on the potential for cancer immune escape or autoimmune events with CTLA-4 and PD-1 blocking antibodies [10–14]. There has also been significant advances in mitogen-activated protein kinase (MAPK) targeted therapies, particularly for BRAF (an intracellular signaling kinase) and MEK (signaling molecule downstream of BRAF). A recent clinical trial demonstrated significant improvement in both relapse-free survival and overall survival with adjuvant dabrafenib (BRAF inhibitor) plus trametinib (MEK inhibitor) in patients with stage III melanoma. These therapies are now approved for adjuvant therapy in BRAF mutated tumors [15]. However, since only approximately 40–50% of melanoma cells harbor an activating BRAF mutation, there still remains a role for IFN-α in this setting as the remaining 50–60% of melanomas would not be susceptible to BRAF-targeted therapies. IFN-α activates the Jak-STAT signaling pathway and induces synthesis of hundreds of different proteins [4, 5]. Our group has shown that STAT1-mediated gene regulation within immune effectors is necessary for mediating the anti-tumor effects of IFN-α and also that the amount IFN-α administered to melanoma patients is likely in excess of the optimal biological dose [4]. Indeed, high doses of IFN-α appear to be no more effective in the induction of phosphorylated STAT1 (p-STAT1) and in the transcription of interferon-stimulated genes (ISGs) than intermediate doses [16, 17]. Our group’s studies in genetically manipulated mice have shown that suppressors of cytokine signaling-1 (SOCS1) and SOCS3 negatively regulate IFN-induced Jak-STAT signal transduction, gene regulation and anti-melanoma activity, and that high doses of IFN-α can induce SOCS proteins [18, 19]. We hypothesized that lower doses of IFN-α would be superior for induction of IFN signal transduction in patient immune cells. A prospective clinical trial was performed wherein patients eligible for adjuvant IFN-α-2b received 1 month of standard intravenous high-dose IFN-α-2b (20 MU/m2) followed by subcutaneous IFN-α-2b at a dose of 10 MU/m2 with dose reductions at set intervals down to a level of 4 MU/m2. Jak-STAT signal transduction and transcription of ISGs in patient peripheral blood mononuclear cells (PBMCs) were monitored during the course of adjuvant IFN-α therapy. The objective of this pilot study was to determine if lower doses of IFN-α were as effective in the induction of IFN signal transduction and gene expression as the standard high dose regimen.