Preclinical evaluation of the simultaneous inhibition of MCL-1 and BCL-2 with the combination of S63845 and venetoclax in multiple myeloma

This work was supported by the Spanish ISCIII-FIS and FEDER Funds (PI 15/00067 and PI 15/02156) and the Regional Health Council of Castilla y León (GRS 1604/A/17). EMA was supported by a grant from the Regional Education Council of Castilla y León co-financed by the European Social Fund

A Comprehensive Patient-Derived Xenograft Collection Representing the Heterogeneity of Melanoma

Therapy of advanced melanoma is changing dramatically. Following mutational and biological subclassification of this heterogeneous cancer, several targeted and immune therapies were approved and increased survival significantly. To facilitate further advancements through pre-clinical in vivo modeling, we have established 459 patient-derived xenografts (PDX) and live tissue samples from 384 patients representing the full spectrum of clinical, therapeutic, mutational, and biological heterogeneity of melanoma. PDX have been characterized using targeted sequencing and protein arrays and are clinically annotated. This exhaustive live tissue resource includes PDX from 57 samples resistant to targeted therapy, 61 samples from responders and non-responders to immune checkpoint blockade, and 31 samples from brain metastasis. Uveal, mucosal, and acral subtypes are represented as well. We show examples of pre-clinical trials that highlight how the PDX collection can be used to develop and optimize precision therapies, biomarkers of response, and the targeting of rare genetic subgroups

The Public Repository of Xenografts enables discovery and randomized phase II-like trials in mice

More than 90% of drugs with preclinical activity fail in human trials, largely due to insufficient efficacy. We hypothesized that adequately powered trials of patient-derived xenografts (PDX) in mice could efficiently define therapeutic activity across heterogeneous tumors. To address this hypothesis, we established a large, publicly available repository of well-characterized leukemia and lymphoma PDXs that undergo orthotopic engraftment, called the Public Repository of Xenografts (PRoXe). PRoXe includes all de-identified information relevant to the primary specimens and the PDXs derived from them. Using this repository, we demonstrate that large studies of acute leukemia PDXs that mimic human randomized clinical trials can characterize drug efficacy and generate transcriptional, functional, and proteomic biomarkers in both treatment-naive and relapsed/refractory disease

PIK3CA mutation uncouples tumor growth and Cyclin D1 regulation from MEK/ERK and mutant KRAS signaling

Mutational activation of KRAS is a common event in human tumors. Identification of the key signaling pathways downstream of mutant KRAS is essential for our understanding of how to pharmacologically target these cancers in patients. We show that PD0325901, a small-molecule MEK inhibitor, decreases MEK/ERK pathway signaling and destabilizes cyclin D1, resulting in significant anticancer activity in a subset of KRAS mutant tumors in vitro and in vivo. Mutational activation of PIK3CA, which commonly co-occurs with KRAS mutation, provides resistance to MEK inhibition through reactivation of AKT signaling. Genetic ablation of the mutant PIK3CA allele in MEK inhibitor–resistant cells restores MEK pathway sensitivity, and re-expression of mutant PIK3CA reinstates the resistance, highlighting the importance of this mutation in resistance to therapy in human cancers. In KRAS mutant tumors, PIK3CA mutation restores cyclin D1 expression and G1-S cell cycle progression so that they are no longer dependent on KRAS and MEK/ERK signaling. Furthermore, the growth of KRAS mutant tumors with coexistent PIK3CA mutations in vivo is profoundly inhibited with combined pharmacologic inhibition of MEK and AKT. These data suggest that tumors with both KRAS and phosphoinositide 3-kinase mutations are unlikely to respond to the inhibition of the MEK pathway alone but will require effective inhibition of both MEK and phosphoinositide 3-kinase/AKT pathway signaling

Mycoplasma infection induces a scleroderma-like centrosome autoantibody response in mice

Development of autoantibodies to intracellular molecules is a universal feature of autoimmune diseases and parallels onset of chronic inflammatory pathology. Initiating antigens of disease-specific autoantibody responses are unknown. We previously showed that the major targets of autoantibodies in scleroderma are centrosomes, organelles involved in mitotic spindle organization. Here we show that centrosome autoantibodies are induced in mice by mycoplasma infection. The centrosome-specific antibody response involves class switching of preexisting IgM to IgG isotypes, suggesting a T cell-dependent mechanism. The antibody response spreads to include additional intracellular targets, with newly recruited autoantibody specificities arising as IgM isotypes. Antibiotic treatment of mice prevents autoantibody development. Centrosome autoantibodies may provide an aetiological link between infection and human autoimmunity and suggest novel therapeutic strategies in these disorders

A novel human protein of the maternal centriole is required for the final stages of cytokinesis and entry into S phase

Centrosomes nucleate microtubules and contribute to mitotic spindle organization and function. They also participate in cytokinesis and cell cycle progression in ways that are poorly understood. Here we describe a novel human protein called centriolin that localizes to the maternal centriole and functions in both cytokinesis and cell cycle progression. Centriolin silencing induces cytokinesis failure by a novel mechanism whereby cells remain interconnected by long intercellular bridges. Most cells continue to cycle, reenter mitosis, and form multicellular syncytia. Some ultimately divide or undergo apoptosis specifically during the protracted period of cytokinesis. At later times, viable cells arrest in G1/G0. The cytokinesis activity is localized to a centriolin domain that shares homology with Nud1p and Cdc11p, budding and fission yeast proteins that anchor regulatory pathways involved in progression through the late stages of mitosis. The Nud1p-like domain of centriolin binds Bub2p, another component of the budding yeast pathway. We conclude that centriolin is required for a late stage of vertebrate cytokinesis, perhaps the final cell cleavage event, and plays a role in progression into S phase

Pharmacokinetic–pharmacodynamic guided optimisation of dose and schedule of CGM097, an HDM2 inhibitor, in preclinical and clinical studies

Background: CGM097 inhibits the p53-HDM2 interaction leading to downstream p53 activation. Preclinical in vivo studies support clinical exploration while providing preliminary evidence for dosing regimens. This first-in-human phase I study aimed at assessing the safety, MTD, PK/PD and preliminary antitumor activity of CGM097 in advanced solid tumour patients (NCT01760525). Methods: Fifty-one patients received oral treatment with CGM097 10-400 mg 3qw (n = 31) or 300-700 mg 3qw 2 weeks on/1 week off (n = 20). Choice of dose regimen was guided by PD biomarkers, and quantitative models describing the effect of CGM097 on circulating platelet and PD kinetics. Results: No dose-limiting toxicities were reported in any regimens. The most common treatment-related grade 3/4 AEs were haematologic events. PK/PD models well described the time course of platelet and serum GDF-15 changes, providing a tool to predict response to CGM097 for dose-limiting thrombocytopenia and GDF-15 biomarker. The disease control rate was 39%, including one partial response and 19 patients in stable disease. Twenty patients had a cumulative treatment duration of >16 weeks, with eight patients on treatment for >32 weeks. The MTD was not determined. Conclusions: Despite delayed-onset thrombocytopenia frequently observed, the tolerability of CGM097 appears manageable. This study provided insights on dosing optimisation for next-generation HDM2 inhibitors. Translational relevance: Haematologic toxicity with delayed thrombocytopenia is a well-known on-target effect of HDM2 inhibitors. Here we have developed a PK/PD guided approach to optimise the dose and schedule of CGM097, a novel HDM2 inhibitor, using exposure, platelets and GDF-15, a known p53 downstream target to predict patients at higher risk to develop thrombocytopenia. While CGM097 had shown limited activity, with disease control rate of 39% and only one patient in partial response, the preliminary data from the first-in-human escalation study together with the PK/PD modeling provide important insights on how to optimize dosing of next generation HDM2 inhibitors to mitigate hematologic toxicity

Combined ALK and MDM2 inhibition increases antitumor activity and overcomes resistance in human ALK mutant neuroblastoma cell lines and xenograft models

The efficacy of ALK inhibitors in patients with ALK-mutant neuroblastoma is limited, highlighting the need to improve their effectiveness in these patients. To this end, we sought to develop a combination strategy to enhance the antitumor activity of ALK inhibitor monotherapy in human neuroblastoma cell lines and xenograft models expressing activated ALK. Herein, we report that combined inhibition of ALK and MDM2 induced a complementary set of anti-proliferative and pro-apoptotic proteins. Consequently, this combination treatment synergistically inhibited proliferation of TP53 wild-type neuroblastoma cells harboring ALK amplification or mutations in vitro, and resulted in complete and durable responses in neuroblastoma xenografts derived from these cells. We further demonstrate that concurrent inhibition of MDM2 and ALK was able to overcome ceritinib resistance conferred by MYCN upregulation in vitro and in vivo. Together, combined inhibition of ALK and MDM2 may provide an effective treatment for TP53 wild-type neuroblastoma with ALK aberrations