Real-world outcomes with ipilimumab and nivolumab in advanced melanoma: a multicentre retrospective study.

PURPOSE: To assess efficacy and toxicity of combination immunotherapy with ipilimumab plus nivolumab in routine practice in a retrospective multicentre cohort of patients with advanced melanoma. PATIENTS AND METHODS: This retrospective analysis included patients with advanced melanoma treated with ipilimumab and nivolumab between October 2015 and January 2020 at six centres in Australia, Europe and the United States of America. We describe efficacy outcomes (overall survival [OS], progression-free survival [PFS] and objective response rate [ORR]) in treatment-naïve and pre-treated patients, with and without brain metastases, plus treatment-related adverse events (trAEs) in all patients treated. RESULTS: A total of 697 patients were identified; 472 were treatment-naïve of which 138 (29.2%) had brain metastases, and 225 were previously treated of which 102 (45.3%) had brain metastases. At baseline, 32.3% had stage M1c and 34.4% stage M1d disease. Lactate dehydrogenase was high in 280 patients (40.2%). With a median follow-up of 25.9 months, median OS in the 334 treatment-naïve patients without brain metastases was 53.7 months (95% confidence interval [CI] 40.8-NR) and 38.7 months (95% CI 18.6-NR) for the 138 treatment-naïve patients with brain metastases. For the entire cohort the ORR was 48%, for treatment-naïve patients without brain metastases ORR was 56.6% with a median PFS of was 13.7 months (95% CI 9.6-26.5). Median PFS was 7.9 months (95% CI 5.8-10.4) and OS 38 months (95% CI 31-NR) for the entire cohort. Grade 3-4 trAE were reported in 44% of patients, and 4 (0.7%) treatment-related deaths (1 pneumonitis, 2 myocarditis and 1 colitis) were recorded. CONCLUSION: The outcome and toxicity of combination immunotherapy with ipilimumab and nivolumab in a real-world patient population are similar to those reported in pivotal trials.

Clinical Models to Define Response and Survival With Anti-PD-1 Antibodies Alone or Combined With Ipilimumab in Metastatic Melanoma.

PURPOSE: Currently, there are no robust biomarkers that predict immunotherapy outcomes in metastatic melanoma. We sought to build multivariable predictive models for response and survival to anti-programmed cell death protein 1 (anti-PD-1) monotherapy or in combination with anticytotoxic T-cell lymphocyte-4 (ipilimumab [IPI]; anti-PD-1 ± IPI) by including routine clinical data available at the point of treatment initiation. METHODS: One thousand six hundred forty-four patients with metastatic melanoma treated with anti-PD-1 ± IPI at 16 centers from Australia, the United States, and Europe were included. Demographics, disease characteristics, and baseline blood parameters were analyzed. The end points of this study were objective response rate (ORR), progression-free survival (PFS), and overall survival (OS). The final predictive models for ORR, PFS, and OS were determined through penalized regression methodology (least absolute shrinkage and selection operator method) to select the most significant predictors for all three outcomes (discovery cohort, N = 633). Each model was validated internally and externally in two independent cohorts (validation-1 [N = 419] and validation-2 [N = 592]) and nomograms were created. RESULTS: The final model for predicting ORR (area under the curve [AUC] = 0.71) in immunotherapy-treated patients included the following clinical parameters: Eastern Cooperative Oncology Group Performance Status, presence/absence of liver and lung metastases, serum lactate dehydrogenase, blood neutrophil-lymphocyte ratio, therapy (monotherapy/combination), and line of treatment. The final predictive models for PFS (AUC = 0.68) and OS (AUC = 0.77) included the same variables as those in the ORR model (except for presence/absence of lung metastases), and included presence/absence of brain metastases and blood hemoglobin. Nomogram calculators were developed from the clinical models to predict outcomes for patients with metastatic melanoma treated with anti-PD-1 ± IPI. CONCLUSION: Newly developed combinations of routinely collected baseline clinical factors predict the response and survival outcomes of patients with metastatic melanoma treated with immunotherapy and may serve as valuable tools for clinical decision making.

Unmasking New Promises: Expanding the Antigen Landscape For Antibody-Drug Conjugates.

Cross-reactivity with normal tissues is one of the key concerns for target selection for antibody-drug conjugates. Probody therapeutics are masked antibodies that can selectively be activated by proteases in the tumor. CX-2029, is a first-in-class Probody targeting CD71 with preliminary efficacy and a tolerable safety profile.See related article by Johnson et al., p. 4521.

Cathepsin S regulates the expression of cathepsin L and the turnover of gamma-interferon-inducible lysosomal thiol reductase in B lymphocytes.

Loading of antigenic peptide fragments on major histocompatibility complex class II molecules is essential for generation of CD4(+) T cell responses and occurs after cathepsin-mediated degradation of the invariant chain chaperone molecule. Cathepsins are expressed differentially in antigen presenting cells, and mice deficient in cathepsin S or cathepsin L exhibit severely impaired antigen presentation in peripheral lymphoid organs and the thymus, respectively. To determine whether these defects are due solely to the block in invariant chain cleavage, we used cathepsin-deficient B cells to examine the role of cathepsins S and B in the degradation of other molecules important in the class II presentation pathway. Our data indicate that neither cathepsin S nor B is critical for H-2M degradation or processing of precursor gamma-interferon-inducible lysosomal thiol reductase (GILT) to a mature thiol reductase, but suggest a role for cathepsin S in the turnover of mature GILT and in regulating levels of mature cathepsin L protein in B cells. Despite the presence of mature cathepsin L protein, no enzyme activity could be detected in B cells or dendritic cells. These experiments suggest a novel mechanism by which these functionally important enzymes may be regulated.

Cutting edge: anti-CD154 therapeutic antibodies induce infectious transplantation tolerance.

Nondepleting anti-CD154 (CD40 ligand) mAbs have proven effective in inducing transplantation tolerance in rodents and primates. In the induction phase, anti-CD154 Ab therapy is known to enhance apoptosis of Ag reactive T cells. However, this may not be the sole explanation for tolerance, as we show in this study that tolerance is maintained through a dominant regulatory mechanism which, like tolerance induced with CD4 Abs, manifests as infectious tolerance. Therefore, tolerance induced with anti-CD154 Abs involves not only the deletion of potentially aggressive T cells, but also a contagious spread of tolerance to new cohorts of graft-reactive T cells as they arise.

High dose bone marrow transplantation induces deletion of antigen-specific T cells in a Fas-independent manner.

BACKGROUND: Monoclonal antibody induced tolerance to high doses of multiple lymphocyte stimulating (MLS)+minor mismatched bone marrow has recently been associated with clonal deletion, as reported in fully allogeneic models of bone marrow transplantation. FasL-induced apoptosis has been shown to mediate antigen-specific T cell deletion after antigenic stimulation in wild-type and T cell receptor transgenic mice. Therefore, we investigate a role for the Fas pathway in deletional tolerance to high dose bone marrow. METHODS: Fas mutant and control mice (H-2k, MLS-1b) were tolerized under the cover of monoclonal antibodies to high dose (5 x 10(7) cells) AKR (H-2k, MLS-1a) bone marrow. Tolerance was confirmed by AKR skin grafting after antibody clearance. Antigen-reactive cell deletion was monitored by Vbeta6+ T cell elimination, measured by flow cytometry of peripheral blood throughout the experiment. Donor T cell (Thy1.1+) chimerism was assessed in a similar manner. RESULTS: Fas mutant mice infused with high dose AKR bone marrow under the cover of antibody were tolerant, as demonstrated by indefinite survival of AKR skin grafts. When high levels of donor cell chimerism were established in Fas mutant mice, peripheral deletion of antigen-reactive cells was observed to be independent of signaling through Fas. CONCLUSIONS: Apoptosis mediated by Fas receptor signaling is not the mechanism of clonal deletion of antigen-reactive cells after antibody facilitated high dose marrow transplantation. However, the Fas mutation does impair the development of adequate donor chimerism.

Dominant tolerance and linked suppression induced by therapeutic antibodies do not depend on Fas-FasL interactions.

BACKGROUND: Nonlytic anti-CD4 monoclonal antibody therapy can be used to induce transplantation tolerance in rodent models. Such tolerance is often associated with dominant regulation, mediated by CD4+ cells, and characterized by infectious tolerance and linked suppression. Understanding the mechanisms by which CD4+ regulatory cells function may improve the manner in which current immunosuppressants are applied and may lead to the development of new tolerance-inducing therapeutics. Fas-mediated apoptosis has been characterized as an important mechanism of peripheral self-tolerance and we here examine whether it has any role in anti-CD4 monoclonal antibody-induced dominant tolerance. METHODS: Tolerance to transplanted skin and bone marrow, mismatched for multiple minor histocompatibility antigens, was induced in Fas mutant and control mice using anti-CD4 and anti-CD8 monoclonal antibodies. To test for linked suppression, animals were transplanted with a second graft-bearing tolerated and third party antigens. The ability of splenocytes from tolerant animals to suppress graft rejection was assessed by transfer into partially immunocompromised recipients. RESULTS: Monoclonal antibody therapy rendered Fas mutant mice tolerant of minor disparate skin and bone marrow. Splenocytes from these and control tolerant animals when transferred into partially immunocompromised Fas mutant or control recipients, induced antigen-specific suppression of graft rejection. Additionally, tolerant Fas mutant mice accepted grafts bearing tolerated and third party antigens. CONCLUSIONS: Signal transduction through the Fas receptor plays no essential role in the induction of tolerance using anti-CD4 and anti-CD8 monoclonal antibodies or its maintenance by active regulation.

CD40 ligand blockade induces CD4+ T cell tolerance and linked suppression.

The CD40-CD40 ligand (CD40L) interaction is a key event in the initiation of an adaptive immune response, and as such the therapeutic value of CD40L blockade has been studied in many experimental models of tissue transplantation and autoimmune disease. In rodents, transplantation of allogeneic tissues under the cover of anti-CD40L Abs has resulted in prolonged graft survival but not tolerance. In this report, we show that failure to induce tolerance probably results from the inability of anti-CD40L Abs to prevent graft rejection elicited by the CD8+ T cell subset. When the CD8+ T cell population is controlled independently, using anti-CD8 Abs, then tolerance is possible. Transplantation tolerance induced by anti-CD4 mAbs can often be associated with dominant regulation, manifested as infectious tolerance and linked suppression, both of which are mediated by CD4+ T cells. We show here that CD4+ T cells rendered tolerant using anti-CD40L therapy exhibit the same regulatory property of linked suppression, as demonstrated by their ability to accept grafts expressing third party Ags only if they are expressed in conjunction with the tolerated Ags. This observation of linked suppression reveals a hitherto undocumented consequence of CD40L blockade that suggests the tolerant state is maintained by a dominant regulatory mechanism. Our results suggest that, although anti-CD40L Abs are attractive clinical immunotherapeutic agents, additional therapies to control aggressive CD8+ T cell responses may be required.

Dominant regulation: a common mechanism of monoclonal antibody induced tolerance?

Transplantation tolerance can be induced by a range of agents that block T cell/antigen-presenting cell (APC) interactions known to be important for initiation of the adaptive immune response. Tolerance so induced has been shown to have a regulatory phenotype dependent on CD4+ cells. This was first observed with nonlytic anti-CD4 antibodies, and was recently demonstrated following other therapeutic approaches. Dominant tolerance also plays a role in natural regulation of the immune response, functioning to prevent autoaggressive cells mediating self-destruction. The mechanism by which dominant tolerance is established and maintained remains unclear, and the reported characteristics of regulatory cells in different experimental models vary widely. Here we review the evidence for potential mechanisms involved and propose that there is a common pathway by which dominant tolerance is mediated.

Bone marrow transplantation induces either clonal deletion or infectious tolerance depending on the dose.

The concept of immunologic tolerance arose from bone marrow transplantation in neonatal or irradiated mice, in which the predominant mechanism is clonal deletion of donor-specific T cells by donor hemopoietic cells in the recipient thymus. A short term treatment with nonlytic CD4 and CD8 mAbs can induce tolerance to tissue allografts or reversal of spontaneous autoimmunity. Such tolerance to skin or heart allografts is dependent on "infectious" tolerance mediated by regulatory CD4+ T cells. We show here, for multiple minor Ag differences, that while a large inoculum of donor marrow produces significant deletion of Ag-reactive cells as expected, a low marrow dose generates tolerance with little evidence of clonal deletion. Only this low dose tolerance can be transferred to unmanipulated recipients via CD4+ T cells, can be passed onto naive T cells as if infectious, and can act to suppress rejection of third party Ags when "linked" on F1 grafts.