Montaser Shaheen

Nivolumab and Ipilimumab versus Ipilimumab in Untreated Melanoma

BACKGROUND In a phase 1 dose-escalation study, combined inhibition of T-cell checkpoint pathways by nivolumab and ipilimumab was associated with a high rate of objective response, including complete responses, among patients with advanced melanoma. METHODS In this double-blind study involving 142 patients with metastatic melanoma who had not previously received treatment, we randomly assigned patients in a 2:1 ratio to receive ipilimumab (3 mg per kilogram of body weight) combined with either nivolumab (1 mg per kilogram) or placebo once every 3 weeks for four doses, followed by nivolumab (3 mg per kilogram) or placebo every 2 weeks until the occurrence of disease progression or unacceptable toxic effects. The primary end point was the rate of investigator-assessed, confirmed objective response among patients with BRAF V600 wild-type tumors. RESULTS Among patients with BRAF wild-type tumors, the rate of confirmed objective response was 61% (44 of 72 patients) in the group that received both ipilimumab and nivolumab (combination group) versus 11% (4 of 37 patients) in the group that received ipilimumab and placebo (ipilimumab-monotherapy group) (P<0.001), with complete responses reported in 16 patients (22%) in the combination group and no patients in the ipilimumab-monotherapy group. The median duration of response was not reached in either group. The median progression-free survival was not reached with the combination therapy and was 4.4 months with ipilimumab monotherapy (hazard ratio associated with combination therapy as compared with ipilimumab monotherapy for disease progression or death, 0.40; 95% confidence interval, 0.23 to 0.68; P<0.001). Similar results for response rate and progression-free survival were observed in 33 patients with BRAF mutation-positive tumors. Drug-related adverse events of grade 3 or 4 were reported in 54% of the patients who received the combination therapy as compared with 24% of the patients who received ipilimumab monotherapy. Select adverse events with potential immunologic causes were consistent with those in a phase 1 study, and most of these events resolved with immune-modulating medication. CONCLUSIONS The objective-response rate and the progression-free survival among patients with advanced melanoma who had not previously received treatment were significantly greater with nivolumab combined with ipilimumab than with ipilimumab monotherapy. Combination therapy had an acceptable safety profile. (Funded by Bristol-Myers Squibb; ClinicalTrials.gov number, NCT01927419.).

Combined nivolumab and ipilimumab versus ipilimumab alone in patients with advanced melanoma: 2-year overall survival outcomes in a multicentre, randomised, controlled, phase 2 trial

BACKGROUND Results from phase 2 and 3 trials in patients with advanced melanoma have shown significant improvements in the proportion of patients achieving an objective response and prolonged progression-free survival with the combination of nivolumab (an anti-PD-1 antibody) plus ipilimumab (an anti-CTLA-4 antibody) compared with ipilimumab alone. We report 2-year overall survival data from a randomised controlled trial assessing this treatment in previously untreated advanced melanoma. METHODS In this multicentre, double-blind, randomised, controlled, phase 2 trial (CheckMate 069) we recruited patients from 19 specialist cancer centres in two countries (France and the USA). Eligible patients were aged 18 years or older with previously untreated, unresectable stage III or IV melanoma and an Eastern Cooperative Oncology Group performance status of 0 or 1. Patients were randomly assigned 2:1 to receive an intravenous infusion of nivolumab 1 mg/kg plus ipilimumab 3 mg/kg or ipilimumab 3 mg/kg plus placebo, every 3 weeks for four doses. Subsequently, patients assigned to nivolumab plus ipilimumab received nivolumab 3 mg/kg every 2 weeks until disease progression or unacceptable toxicity, whereas patients allocated to ipilimumab alone received placebo every 2 weeks during this phase. Randomisation was done via an interactive voice response system with a permuted block schedule (block size of six) and stratification by BRAF mutation status. The study funder, patients, investigators, and study site staff were masked to treatment assignment. The primary endpoint, which has been reported previously, was the proportion of patients with BRAFV600 wild-type melanoma achieving an investigator-assessed objective response. Overall survival was an exploratory endpoint and is reported in this Article. Efficacy analyses were done on the intention-to-treat population, whereas safety was assessed in all treated patients who received at least one dose of study drug. This study is registered with ClinicalTrials.gov, number NCT01927419, and is ongoing but no longer enrolling patients. FINDINGS Between Sept 16, 2013, and Feb 6, 2014, we screened 179 patients and enrolled 142, randomly assigning 95 patients to nivolumab plus ipilimumab and 47 to ipilimumab alone. In each treatment group, one patient no longer met the study criteria following randomisation and thus did not receive study drug. At a median follow-up of 24·5 months (IQR 9·1-25·7), 2-year overall survival was 63·8% (95% CI 53·3-72·6) for those assigned to nivolumab plus ipilimumab and 53·6% (95% CI 38·1-66·8) for those assigned to ipilimumab alone; median overall survival had not been reached in either group (hazard ratio 0·74, 95% CI 0·43-1·26; p=0·26). Treatment-related grade 3-4 adverse events were reported in 51 (54%) of 94 patients who received nivolumab plus ipilimumab compared with nine (20%) of 46 patients who received ipilimumab alone. The most common treatment-related grade 3-4 adverse events were colitis (12 [13%] of 94 patients) and increased alanine aminotransferase (ten [11%]) in the combination group and diarrhoea (five [11%] of 46 patients) and hypophysitis (two [4%]) in the ipilimumab alone group. Serious grade 3-4 treatment-related adverse events were reported in 34 (36%) of 94 patients who received nivolumab plus ipilimumab (including colitis in ten [11%] of 94 patients, and diarrhoea in five [5%]) compared with four (9%) of 46 patients who received ipilimumab alone (including diarrhoea in two [4%] of 46 patients, colitis in one [2%], and hypophysitis in one [2%]). No new types of treatment-related adverse events or treatment-related deaths occurred in this updated analysis. INTERPRETATION Although follow-up of the patients in this study is ongoing, the results of this analysis suggest that the combination of first-line nivolumab plus ipilimumab might lead to improved outcomes compared with first-line ipilimumab alone in patients with advanced melanoma. The results suggest encouraging survival outcomes with immunotherapy in this population of patients. FUNDING Bristol-Myers Squibb.

Methylation of histone H3 lysine 36 enhances DNA repair by nonhomologous end-joining

Given its significant role in the maintenance of genomic stability, histone methylation has been postulated to regulate DNA repair. Histone methylation mediates localization of 53BP1 to a DNA double-strand break (DSB) during homologous recombination repair, but a role in DSB repair by nonhomologous end-joining (NHEJ) has not been defined. By screening for histone methylation after DSB induction by ionizing radiation we found that generation of dimethyl histone H3 lysine 36 (H3K36me2) was the major event. Using a novel human cell system that rapidly generates a single defined DSB in the vast majority of cells, we found that the DNA repair protein Metnase (also SETMAR), which has a SET histone methylase domain, localized to an induced DSB and directly mediated the formation of H3K36me2 near the induced DSB. This dimethylation of H3K36 improved the association of early DNA repair components, including NBS1 and Ku70, with the induced DSB, and enhanced DSB repair. In addition, expression of JHDM1a (an H3K36me2 demethylase) or histone H3 in which K36 was mutated to A36 or R36 to prevent H3K36me2 formation decreased the association of early NHEJ repair components with an induced DSB and decreased DSB repair. Thus, these experiments define a histone methylation event that enhances DNA DSB repair by NHEJ.

Synthetic lethality: exploiting the addiction of cancer to DNA repair

Because cancer at its origin must acquire permanent genomic mutations, it is by definition a disease of DNA repair. Yet for cancer cells to replicate their DNA and divide, which is the fundamental phenotype of cancer, multiple DNA repair pathways are required. This produces a paradox for the cancer cell, where its origin is at the same time its weakness. To overcome this difficulty, a cancer cell often becomes addicted to DNA repair pathways other than the one that led to its initial mutability. The best example of this is in breast or ovarian cancers with mutated BRCA1 or 2, essential components of a repair pathway for repairing DNA double-strand breaks. Because replicating DNA requires repair of DNA double-strand breaks, these cancers have become reliant on another DNA repair component, PARP1, for replication fork progression. The inhibition of PARP1 in these cells results in catastrophic double-strand breaks during replication, and ultimately cell death. The exploitation of the addiction of cancer cells to a DNA repair pathway is based on synthetic lethality and has wide applicability to the treatment of many types of malignancies, including those of hematologic origin. There is a large number of novel compounds in clinical trials that use this mechanism for their antineoplastic activity, making synthetic lethality one of the most important new concepts in recent drug development.

Metnase/SETMAR: a domesticated primate transposase that enhances DNA repair, replication, and decatenation

Metnase is a fusion gene comprising a SET histone methyl transferase domain and a transposase domain derived from the Mariner transposase. This fusion gene appeared first in anthropoid primates. Because of its biochemical activities, both histone (protein) methylase and endonuclease, we termed the protein Metnase (also called SETMAR). Metnase methylates histone H3 lysine 36 (H3K36), improves the integration of foreign DNA, and enhances DNA double-strand break (DSB) repair by the non-homologous end joining (NHEJ) pathway, potentially dependent on its interaction with DNA Ligase IV. Metnase interacts with PCNA and enhances replication fork restart after stalling. Metnase also interacts with and stimulates TopoIIα-dependent chromosome decatenation and regulates cellular sensitivity to topoisomerase inhibitors used as cancer chemotherapeutics. Metnase has DNA nicking and endonuclease activity that linearizes but does not degrade supercoiled plasmids. Metnase has many but not all of the properties of a transposase, including Terminal Inverted Repeat (TIR) sequence-specific DNA binding, DNA looping, paired end complex formation, and cleavage of the 5′ end of a TIR, but it cannot efficiently complete transposition reactions. Interestingly, Metnase suppresses chromosomal translocations. It has been hypothesized that transposase activity would be deleterious in primates because unregulated DNA movement would predispose to malignancy. Metnase may have been selected for in primates because of its DNA repair and translocation suppression activities. Thus, its transposase activities may have been subverted to prevent deleterious DNA movement.

Metnase Mediates Resistance to Topoisomerase II Inhibitors in Breast Cancer Cells

DNA replication produces tangled, or catenated, chromatids, that must be decatenated prior to mitosis or catastrophic genomic damage will occur. Topoisomerase IIα (Topo IIα) is the primary decatenating enzyme. Cells monitor catenation status and activate decatenation checkpoints when decatenation is incomplete, which occurs when Topo IIα is inhibited by chemotherapy agents such as the anthracyclines and epididophyllotoxins. We recently demonstrated that the DNA repair component Metnase (also called SETMAR) enhances Topo IIα-mediated decatenation, and hypothesized that Metnase could mediate resistance to Topo IIα inhibitors. Here we show that Metnase interacts with Topo IIα in breast cancer cells, and that reducing Metnase expression significantly increases metaphase decatenation checkpoint arrest. Repression of Metnase sensitizes breast cancer cells to Topo IIα inhibitors, and directly blocks the inhibitory effect of the anthracycline adriamycin on Topo IIα-mediated decatenation in vitro. Thus, Metnase may mediate resistance to Topo IIα inhibitors, and could be a biomarker for clinical sensitivity to anthracyclines. Metnase could also become an important target for combination chemotherapy with current Topo IIα inhibitors, specifically in anthracycline-resistant breast cancer.

Targeting the transposase domain of the DNA repair component Metnase to enhance chemotherapy.

Previous studies have shown that the DNA repair component Metnase (SETMAR) mediates resistance to DNA damaging cancer chemotherapy. Metnase has a nuclease domain that shares homology with the Transposase family. We therefore virtually screened the tertiary Metnase structure against the 550,000 compound ChemDiv library to identify small molecules that might dock in the active site of the transposase nuclease domain of Metnase. We identified eight compounds as possible Metnase inhibitors. Interestingly, among these candidate inhibitors were quinolone antibiotics and HIV integrase inhibitors, which share common structural features. Previous reports have described possible activity of quinolones as antineoplastic agents. Therefore, we chose the quinolone ciprofloxacin for further study, based on its wide clinical availability and low toxicity. We found that ciprofloxacin inhibits the ability of Metnase to cleave DNA and inhibits Metnase-dependent DNA repair. Ciprofloxacin on its own did not induce DNA damage, but it did reduce repair of chemotherapy-induced DNA damage. Ciprofloxacin increased the sensitivity of cancer cell lines and a xenograft tumor model to clinically relevant chemotherapy. These studies provide a mechanism for the previously postulated antineoplastic activity of quinolones, and suggest that ciprofloxacin might be a simple yet effective adjunct to cancer chemotherapy.

Endocrine-related adverse events associated with immune checkpoint blockade and expert insights on their management

Agents that modulate immune checkpoint proteins, such as cytotoxic T-lymphocyte antigen-4 (CTLA-4) and programmed death receptor-1 (PD-1), have become a mainstay in cancer treatment. The clinical benefit afforded by immune checkpoint inhibitors can be accompanied by immune-related adverse events (irAE) that affect the skin, gastrointestinal tract, liver, and endocrine system. The types of irAEs associated with immune checkpoint inhibitors are generally consistent across tumor types. Immune-related endocrine events can affect the pituitary, thyroid, and adrenal glands, as well as other downstream target organs. These events are unique when compared with other irAEs because the manifestations are often irreversible. Immune-related endocrine events are typically grade 1/2 in severity and often present with non-specific symptoms, making them difficult to diagnose. The mechanisms underlying immune-related target organ damage in select individuals remain mostly undefined. Management includes close patient monitoring, appropriate laboratory testing for endocrine function, replacement of hormones, and consultation with an endocrinologist when appropriate. An awareness of the symptoms and management of immune-related endocrine events may aid in the safe and appropriate use of immune checkpoint inhibitors in clinical practice.

The Role of PCNA Posttranslational Modifications in Translesion Synthesis

Organisms are predisposed to different types in DNA damage. Multiple mechanisms have evolved to deal with the individual DNA lesions. Translesion synthesis is a special pathway that enables the replication fork to bypass blocking lesions. Proliferative Cell Nuclear Antigen (PCNA), which is an essential component of the fork, undergoes posttranslational modifications, particularly ubiquitylation and sumoylation that are critical for lesion bypass and for filling of DNA gaps which result from this bypass. A special ubiquitylation system, represented by the Rad6 group of ubiquitin conjugating and ligating enzymes, mediates PCNA mono- and polyubiquitylation in response to fork stalling. The E2 SUMO conjugating enzyme Ubc9 and the E3 SUMO ligase Siz1 are responsible for PCNA sumoylation during undisturbed S phase and in response to fork stalling as well. PCNA monoubiquitylation mediated by Rad6/Rad18 recruits special polymerases to bypass the lesion and fill in the DNA gaps. PCNA polyubiquitylation achieved by ubc13-mms2/Rad 5 in yeast mediates an error-free pathway of lesion bypass likely through template switch. PCNA sumoylation appears required for this error-free pathway, and it plays an antirecombinational role during normal replication by recruiting the helicase Srs2 to prevent sister chromatid exchange and hyper-recombination.

Tumor microenvironment changes leading to resistance of immune checkpoint inhibitors in metastatic melanoma and strategies to overcome resistance

&NA; Immunotherapy with checkpoint inhibitors targeting CTLA‐4 and/or PD‐1 receptors independent of the BRAF mutational status and targeted therapy with BRAF and MEK inhibitors in BRAF V600 mutated patients have taken the forefront of advanced melanoma treatment. The main advantage of immunotherapy is its ability to provide durable responses in a subset of patients. However, significant proportions of patients either do not respond or have progression after initial response to immunotherapies. Multiple changes in the tumor microenvironment, such as down regulation of immune checkpoint ligands by tumor, alteration in interferon signaling, and activation of alternate immune suppressive pathways, have been identified as possible reasons for failure of immune checkpoint therapy. Here, we review the resistance mechanisms adopted by cancer cells to checkpoint inhibitor therapy and targeted therapy. In addition, we focus on the available and emerging evidence on tumor microenvironment modulation by BRAF/MEK inhibitor therapy and its role in improving responses to checkpoint inhibitor therapy. Graphical abstract Figure. No caption available.