Secondary resistance to immunotherapy associated with β-catenin pathway activation or PTEN loss in metastatic melanoma

Background

While cancer immunotherapies including checkpoint blockade antibodies, adoptive T cell therapy, and even some vaccines have given rise to major clinical responses with durability in many cases, a subset of patients who initially respond subsequently develop secondary resistance to therapy. Tumor-intrinsic mechanisms of acquired immunotherapy resistance are incompletely understood.

Methods

Baseline and treatment-resistant tumors underwent molecular analysis via transcriptional profiling or genomic sequencing for oncogenic alterations and histologic analysis for T cell infiltration to investigate mechanisms contributing to T cell exclusion and acquired resistance to immunotherapy.

Results

We describe two patients with metastatic melanoma who initially showed a durable partial response to either a melanoma-peptide/interleukin-12 vaccine or combined anti-CTLA-4 + anti-PD-1 therapy, but subsequently developed new treatment-resistant metastases. In the first case, the recurrent tumor showed new robust tumor expression of β-catenin, whereas in the second case genomic sequencing revealed acquired PTEN loss. Both cases were associated with loss of T cell infiltration, and both pathways have been mechanistically linked to immune resistance preclinically.

Conclusion

Our results suggest that secondary resistance to immunotherapies can arise upon selection for new oncogenic variants that mediate T cell exclusion. To identify the spectrum of underlying mechanisms of therapeutic resistance, similar evaluation for the emergence of tumor-intrinsic alterations in resistant lesions should be done prospectively at the time of relapse in a range of additional patients developing secondary resistance.

Single dose denileukin diftitox does not enhance vaccine-induced T cell responses or effectively deplete Tregs in advanced melanoma: immune monitoring and clinical results of a randomized phase II trial

Background

Depletion of CD25⁺ Tregs improves anti-tumor immunity in preclinical models. Denileukin diftitox is a recombinant fusion protein of human IL-2 and diptheria toxin fragment that also can kill CD25⁺ T cells. Prior clinical trials of denileukin diftitox suggested reduction of FoxP3⁺ Tregs and some clinical responses.

Method

To investigate the immunologic effects of denileukin difitox on vaccine-specific immune responses in melanoma, a randomized clinical trial of single dose denileukin diftitox prior to vaccination versus vaccination alone in subjects with HLA-A2⁺ metastatic melanoma was performed. Treatment included randomization to a 4-peptide vaccine (Melan-A, gp100, MAGE3 and NA17 with GM-CSF emulsified in Montanide) alone or after single dose of denileukin diftitox (18 mcg/kg). Vaccine was given every 2 weeks for 3 doses and, absent clinical progression, continued every 2 weeks. Blood and tumor biopsies were obtained pretreatment and after 3 vaccinations for immunologic assessments.

Results

In 17 treated subjects there were no drug-related G3-4 adverse events. One partial response and 8 stable disease were observed in 9 subjects (4 DD: 5 vaccine only) with no impact of denileukin diftitox on time to progression. Total peripheral Tregs were not significantly altered, and in 1 patient biopsy intra-tumoral FoxP3 transcripts were not reduced following denileukin diftitox. ELISA for IL2R-α demonstrated no impact on outcomes by soluble CD25 level. Immune monitoring suggested the development of modest vaccine-specific CD8⁺ T cell responses in the control group, however immunization efficacy was actually reduced in the denileukin diftitox group.

Conclusion

Our results indicate that denileukin diftitox did not effectively deplete Tregs, augment T cell responses, or improve clinical activity in melanoma. Clinicaltrials.gov ID: NCT00515528; Registered August 9, 2007.

Randomized phase II trial of multipeptide vaccination with or without a single pre-vaccine dose of denileukin diftitox in advanced melanoma

2582

Background: The efficacy of immunotherapy approaches such as vaccines in melanoma appears limited, in part, due to immune suppressive mechanisms in the tumor microenvironment. One of these mechanisms is the presence of CD4+CD25+FoxP3+ regulatory T cells (Tregs). It has been hypothesized that strategies to reduce Treg numbers should improve the efficacy of melanoma vaccines. Methods: The study design was to randomize 24 HLA-A2+ patients to receive vaccine alone or denileukin diftitox (18 mcg/kg i.v.) as a single dose 4 days prior to the first vaccination. The vaccine formulation consisted of 4 melanoma antigen peptides (derived from MelanA, gp100, MAGE3, and NA17A) emulsified in Montanide and GM-CSF, administered i.d./s.c. every 2 weeks. The primary endpoints were assessment of depletion of Tregs from the peripheral blood, and measurement of antigen-specific CD8+ T cell responses by ELISPOT. Secondary endpoints included clinical response and analyses of the tumor microenvironment for changes in Treg infiltration. Results: The treatment was well tolerated. Enrollment was halted at 16 patients when it was clear that immune response endpoints would not be reached. There was no significant decrease in Treg numbers, nor was there an increase in vaccine-induced T cell responses, when patients received denileukin diftitox prior to vaccination. In patients with biopsiable tumors, there was no decrease in Tregs in metastatic lesions post-versus-pre-treatment. Of the 9 patients who showed clinical benefit (1 PR, 8 SD), 4 of them received denileukin diftitox and 5 did not. Estimated time to progression was 146 days in the group that received denileukin diftitox and 131 days in the group that did not. Conclusions: Denileukin diftitox given as a single dose prior to vaccination was not sufficient to deplete Tregs or improve the potency of this melanoma vaccine. Alternative strategies to reduce Tregs, such as multiple doses of denileukin diftitox or anti-CD25 mAbs, should be considered.

Phase II study of the anti-ganglioside GD3 mouse/human chimeric antibody KW2871 combined with high dose interferon-a2b in patients with metastatic melanoma

8547

Background: Immunotherapy has demonstrated notable effects in metastatic melanoma (MM) with durable responses achieved by high-dose IL-2 and IFNα2b, leading to approval of these therapies for treatment of melanoma. However, complete responses occur in only a minority of patients. KW2871 is a chimeric monoclonal antibody (mAb) targeting the GD3 ganglioside with demonstrated antitumor activity and enhancement of antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). IFNα2b has potent immunoregulatory, anti-proliferative, differentiation-inducing, pro-apoptotic, and anti-angiogenic properties against a variety of malignancies including melanoma. Combining high dose IFNα2b (HDI) + KW2871 was hypothesized to have synergistic anti-tumor activity due to (1) the ability of HDI to enhance KW2871 induced ADCC in vitro (Liu, Cancer Immun 2002); (2) improved mAb targeting due to increased GD3 expression and induced inflammatory cytokines (TNF-α, IL-4 and IFN-γ) (Hoon, Cancer Res, 1991); (3) increased tumor-infiltrating immune cells (Kirkwood, Cancer 2002; Moschos, J Clin Oncol 2006). Methods: This is an open label, dose-escalation, phase II study of KW2871 plus HDI in patients with measurable MM. Primary objectives are progression-free survival (PFS) and safety. Secondary objectives include assessment for tumor response by RECIST, ADCC, CDC, pharmacokinetics, human antichimeric antibodies (HACA), tumor-infiltrating immune cells, biomarkers and OS. Patients with measurable disease by RECIST, stable brain metastases, and performance status ECOG 0 or 1 are eligible. Patients with severe comorbidities or autoimmune disease or prior exposure to anti-GD3 antibodies are excluded. Sequential enrollment to cohorts of KW2871 at 5, 10 , 20 mg/m2 IV every 2 week in combination with HDI 20 MU/m2 IV once daily x 5 Days for 4 weeks, then 10 MU/m2 SC three times weekly until disease progression. Results: To date, Cohort 1 (5 mg/m2 KW2871) and Cohort 2 (10 mg/m2 KW2871) have been completed safely. Cohort 3 (20 mg/m2 KW2871) has enrolled of 18 of 27 planned patients. Conclusions: Will be presented at study completion.

Phase II Multicenter Study of Neoadjuvant Biochemotherapy for Patients With Stage III Malignant Melanoma

Purpose

To determine the relapse-free survival, overall survival, and response rate of patients with stage III melanoma treated with neoadjuvant biochemotherapy in a multicenter setting.

Patients and Methods

Patients with pathologically proven stage III melanoma, either via clinical detection or sentinel lymph node positivity, were eligible for enrollment. Patients received two cycles of preoperative biochemotherapy followed by complete regional lymphadenectomy and two postoperative courses of biochemotherapy. The biochemotherapy regimen consisted of the following: cisplatin 20 mg/m2 on days 1 to 4, dacarbazine 800 mg/m2 on day 1 only, vinblastine 1.6 mg/m2 on days 1 to 4, interleukin-2 total dose of 36 MU/m2 during 4 days, and interferon alfa 5 MU/m2 on days 1 to 5. Growth factor support was administered with each cycle.

Results

Ninety-two patients were eligible for the study. At a median follow-up of 40.4 months, relapse-free survival and overall survival are 64% and 78%, respectively. There was a lower relapse rate and improved survival for patients with a positive sentinel lymph node compared with patients with clinically detected lymph nodes, although this difference did not reach statistical significance. Of the 50 patients with measurable disease, the overall response rate was 26%. Toxicity of the biochemotherapy was high but generally manageable.

Conclusion

The current study has expanded the preliminary evidence on neoadjuvant biochemotherapy for stage III melanoma.