An Open-label Phase I Study of GDC-0927 in Postmenopausal Women with Locally Advanced or Metastatic Estrogen Receptor-Positive Breast Cancer.

PURPOSE: GDC-0927 is a novel, potent, nonsteroidal, orally bioavailable, selective estrogen receptor (ER) degrader that induces tumor regression in ER+ breast cancer xenograft models. PATIENTS AND METHODS: This phase I dose-escalation multicenter study enrolled postmenopausal women with ER+/HER2- metastatic breast cancer to determine the safety, pharmacokinetics, and recommended phase II dose of GDC-0927. Pharmacodynamics was assessed with [18F]-fluoroestradiol (FES) PET scans. RESULTS: Forty-two patients received GDC-0927 once daily. The MTD was not reached. The most common adverse events (AE) regardless of causality were nausea, constipation, diarrhea, arthralgia, fatigue, hot flush, back pain, and vomiting. There were no deaths, grade 4/5 AEs, or treatment-related serious AEs. Two patients experienced grade 2 AEs of special interest of deep vein thrombosis and jugular vein thrombosis, both considered unrelated to GDC-0927. Following dosing, approximately 1.6-fold accumulation was observed, consistent with the observed half-life and dosing frequency. There were no complete or partial responses. Pharmacodynamics was supported by >90% reduction in FES uptake and an approximately 40% reduction in ER expression, suggesting ER degradation is not the mechanistic driver of ER antagonism. Twelve patients (29%) achieved clinical benefit; 17 patients (41%) showed a confirmed best overall response of stable disease. Baseline levels of ER and progesterone receptor protein and mutant ESR1 circulating tumor DNA did not correlate with clinical benefit. CONCLUSIONS: GDC-0927 appeared to be well tolerated with pharmacokinetics supporting once-daily dosing. There was evidence of target engagement and preliminary evidence of antitumor activity in heavily pretreated patients with advanced/metastatic ER+/HER2- breast cancer with and without ESR1 mutations.

Multimeric Anti-DR5 IgM Agonist Antibody IGM-8444 Is a Potent Inducer of Cancer Cell Apoptosis and Synergizes with Chemotherapy and BCL-2 Inhibitor ABT-199.

Death receptor 5 (DR5) is an attractive target for cancer therapy due to its broad upregulated expression in multiple cancers and ability to directly induce apoptosis. Though anti-DR5 IgG antibodies have been evaluated in clinical trials, limited efficacy has been attributed to insufficient receptor crosslinking. IGM-8444 is an engineered, multivalent agonistic IgM antibody with 10 binding sites to DR5 that induces cancer cell apoptosis through efficient DR5 multimerization. IGM-8444 bound to DR5 with high avidity and was substantially more potent than an IgG with the same binding domains. IGM-8444 induced cytotoxicity in a broad panel of solid and hematologic cancer cell lines but did not kill primary human hepatocytes in vitro, a potential toxicity of DR5 agonists. In multiple xenograft tumor models, IGM-8444 monotherapy inhibited tumor growth, with strong and sustained tumor regression observed in a gastric PDX model. When combined with chemotherapy or the BCL-2 inhibitor ABT-199, IGM-8444 exhibited synergistic in vitro tumor cytotoxicity and enhanced in vivo efficacy, without augmenting in vitro hepatotoxicity. These results support the clinical development of IGM-8444 in solid and hematologic malignancies as a monotherapy and in combination with chemotherapy or BCL-2 inhibition.

An open-label phase I dose-escalation study of the safety and pharmacokinetics of DMUC4064A in patients with platinum-resistant ovarian cancer.

OBJECTIVES: MUC16 is overexpressed in the majority of human epithelial ovarian cancers (OC). DMUC4064A is a humanized anti-MUC16 monoclonal antibody conjugated to the microtubule-disrupting agent monomethyl auristatin E. This trial assessed the safety, tolerability, pharmacokinetics, and preliminary activity of DMUC4064A in patients with platinum-resistant OC. METHODS: DMUC4064A was administered once every 3 weeks to patients in 1.0-5.6 mg/kg dose escalation cohorts, followed by cohort expansion at the recommended Phase II dose (RP2D). RESULTS: Sixty-five patients were enrolled and received a median of 5 cycles (range 1-20) of DMUC4064A. The maximum tolerated dose was not reached; 5.2 mg/kg was the RP2D based on the overall tolerability profile. The most common adverse events were fatigue, nausea, abdominal pain, constipation, blurred vision, diarrhea, and anemia. Sixteen patients (25%) experienced related grade ≥ 3 toxicities. Twenty-six patients (40%) experienced ocular toxicities. The exposure of acMMAE was dose proportional, with a half-life of ~6 days. Sixteen patients (25%) experienced confirmed objective partial response (PR or CR) starting at ≥3.2 mg/kg dose levels, while 23 (35%) patients had best responses of PR or CR. Overall, the clinical benefit rate was 42% (27 patients with a best response [confirmed and unconfirmed] of CR, or PR or SD lasting ≥6 months). Among the 54 patients with high MUC16 immunohistochemistry scores, the clinical benefit rate was 46% (25 patients). Median progression-free survival was 3.9 months overall. CONCLUSIONS: In this Phase I study, DMUC4064A demonstrated a tolerable safety profile along with encouraging efficacy in the indication of platinum-resistant OC.

Phase 1b study of anti-NaPi2b antibody-drug conjugate lifastuzumab vedotin (DNIB0600A) in patients with platinum-sensitive recurrent ovarian cancer.

OBJECTIVE: This study investigated the safety and tolerability of lifastuzumab vedotin (DNIB0600A) (LIFA), an antibody-drug conjugate, in patients with recurrent platinum-sensitive ovarian cancer (PSOC). METHODS: In this open-label, multicenter phase 1b study, LIFA was administered intravenously once every 3 weeks (Q3W) with starting dose 1.2 mg/kg in a 3 + 3 dose-escalation scheme. All patients received carboplatin at dose AUC 6 mg/mL·min (AUC6) Q3W for up to 6 cycles. Dose expansion cohorts were enrolled ± bevacizumab 15 mg/kg Q3W. RESULTS: Patients received LIFA at 1.2, 1.8, and 2.4 mg (n = 4, 5, and 20, respectively) with carboplatin. The maximum tolerated dose was not reached. The recommended phase 2 dose (RP2D) was LIFA 2.4 mg/kg + carboplatin AUC6 (cycles 1-6), with or without bevacizumab 15 mg/kg. Twelve patients received RP2D with bevacizumab. All patients experienced ≥1 adverse event (AE). The most common treatment-related AEs were neutropenia, peripheral neuropathy, thrombocytopenia, nausea, fatigue, anemia, diarrhea, vomiting, hypomagnesaemia, aspartate aminotransferase increased, alanine aminotransferase increased, and alopecia. Thirty-four (83%) patients experienced grade ≥ 3 AEs, the most frequent of which were neutropenia and thrombocytopenia. Nine (22%) patients experienced serious AEs. Pulmonary toxicities (34%), considered a potential risk of LIFA, included one patient who discontinued study treatment due to grade 2 pneumonitis. The median duration of progression-free survival was 10.71 months (95% CI: 8.54, 13.86) with confirmed complete/partial responses in 24 (59%) patients. Pharmacokinetics of mono-therapy LIFA was similar in combination therapy. CONCLUSION: LIFA in combination with carboplatin ± bevacizumab demonstrated acceptable safety and encouraging activity in PSOC patients.

Phase Ia Study of Anti-NaPi2b Antibody-Drug Conjugate Lifastuzumab Vedotin DNIB0600A in Patients with Non-Small Cell Lung Cancer and Platinum-Resistant Ovarian Cancer.

PURPOSE: This phase I trial assessed the safety, tolerability, and preliminary antitumor activity of lifastuzumab vedotin (LIFA), an antibody-drug conjugate of anti-NaPi2b mAb (MNIB2126A) and a potent antimitotic agent (monomethyl auristatin E). PATIENTS AND METHODS: LIFA was administered to patients with non-small cell lung cancer (NSCLC) and platinum-resistant ovarian cancer (PROC), once every 3 weeks, by intravenous infusion. The starting dose was 0.2 mg/kg in this 3+3 dose-escalation design, followed by cohort expansion at the recommended phase II dose (RP2D). RESULTS: Overall, 87 patients were treated at doses between 0.2 and 2.8 mg/kg. The MTD was not reached; 2.4 mg/kg once every 3 weeks was selected as the RP2D based on overall tolerability profile. The most common adverse events of any grade and regardless of relationship to study drug were fatigue (59%), nausea (49%), decreased appetite (37%), vomiting (32%), and peripheral sensory neuropathy (29%). Most common treatment-related grade ≥3 toxicities among patients treated at the RP2D (n = 63) were neutropenia (10%), anemia (3%), and pneumonia (3%). The pharmacokinetic profile was dose proportional. At active doses ≥1.8 mg/kg, partial responses were observed in four of 51 (8%) patients with NSCLC and 11 of 24 (46%) patients with PROC per RECIST. All RECIST responses occurred in patients with NaPi2b-high by IHC. The CA-125 biomarker assessed for patients with PROC dosed at ≥1.8 mg/kg showed 13 of 24 (54%) had responses (≥50% decline from baseline). CONCLUSIONS: LIFA exhibited dose-proportional pharmacokinetics and an acceptable safety profile, with encouraging activity in patients with PROC at the single-agent RP2D of 2.4 mg/kg.

Phase I study of the anti-FcRH5 antibody-drug conjugate DFRF4539A in relapsed or refractory multiple myeloma.

FcRH5 is a cell surface marker enriched on malignant plasma cells when compared to other hematologic malignancies and normal tissues. DFRF4539A is an anti-FcRH5 antibody-drug conjugated to monomethyl auristatin E (MMAE), a potent anti-mitotic agent. This phase I study assessed safety, tolerability, maximum tolerated dose (MTD), anti-tumor activity, and pharmacokinetics of DFRF4539A in patients with relapsed/refractory multiple myeloma. DFRF4539A was administered at 0.3-2.4 mg/kg every 3 weeks or 0.8-1.1 mg/kg weekly as a single-agent by intravenous infusion to 39 patients. Exposure of total antibody and antibody-conjugate-MMAE analytes was linear across the doses tested. There were 37 (95%) adverse events (AEs), 8 (21%) serious AEs, and 15 (39%) AEs ≥ grade 3. Anemia (n = 10, 26%) was the most common AE considered related to DFRF4539A. Two cases of grade 3 acute renal failure were attributed to DFRF4539A. There were no deaths; the MTD was not reached. DFRF4539A demonstrated limited activity in patients at the doses tested with 2 (5%) partial response, 1 (3%) minimal response, 18 (46%) stable disease, and 16 (41%) progressive disease. FcRH5 was confirmed to be expressed and occupied by antibody post-treatment and thus remains a valid myeloma target. Nevertheless, this MMAE-based antibody-drug-conjugate targeting FcRH5 was unsuccessful for myeloma.

High-Throughput and Sensitive Quantification of Circulating Tumor DNA by Microfluidic-Based Multiplex PCR and Next-Generation Sequencing.

Circulating tumor DNA (ctDNA) has potential to serve as a biomarker for noninvasive monitoring of treatment response and disease progression. However, broad clinical applicability of ctDNA has been limited by the low sensitivity, throughput, and patient coverage offered by existing ctDNA detection methods. Herein, we report the adaptation and characterization of the microfluidics multiplex PCR sequencing technology for high-throughput and sensitive quantitation of ctDNA. A multiplex PCR preamplification step was developed and incorporated into the microfluidics multiplex PCR sequencing work flow to enable low-input ctDNA analysis with enhanced sensitivity. An empirical bayesian model was developed to characterize both position and substitution-associated system errors specific to this platform and provided a tailored approach to greatly enhance the confidence and accuracy of variant calling for ctDNA analysis. Clinical validation of this platform for ctDNA mutation detection demonstrated an overall sensitivity of 92% and specificity of 100% when using mutation calls in the matched tumor tissues as a benchmark. Finally, we established an early proof of concept of clinical utility of this ctDNA work flow for monitoring disease progression using clinical trial samples. Our novel ctDNA work flow provides a high-throughput and sensitive platform that can be implemented in clinical trials for mutation detection and disease monitoring from plasma ctDNA.

Gli protein activity is controlled by multisite phosphorylation in vertebrate Hedgehog signaling.

Gli proteins are transcriptional effectors of the Hedgehog (Hh) pathway in both normal development and cancer. We describe a program of multisite phosphorylation that regulates the conversion of Gli proteins into transcriptional activators. In the absence of Hh ligands, Gli activity is restrained by the direct phosphorylation of six conserved serine residues by protein kinase A (PKA), a master negative regulator of the Hh pathway. Activation of signaling leads to a global remodeling of the Gli phosphorylation landscape: the PKA target sites become dephosphorylated, while a second cluster of sites undergoes phosphorylation. The pattern of Gli phosphorylation can regulate Gli transcriptional activity in a graded fashion, suggesting a phosphorylation-based mechanism for how a gradient of Hh signaling in a morphogenetic field can be converted into a gradient of transcriptional activity.

Isolation and mutational analysis of circulating tumor cells from lung cancer patients with magnetic sifters and biochips.

Detection and characterization of circulating tumor cells (CTCs) may reveal insights into the diagnosis and treatment of malignant disease. Technologies for isolating CTCs developed thus far suffer from one or more limitations, such as low throughput, inability to release captured cells, and reliance on expensive instrumentation for enrichment or subsequent characterization. We report a continuing development of a magnetic separation device, the magnetic sifter, which is a miniature microfluidic chip with a dense array of magnetic pores. It offers high efficiency capture of tumor cells, labeled with magnetic nanoparticles, from whole blood with high throughput and efficient release of captured cells. For subsequent characterization of CTCs, an assay, using a protein chip with giant magnetoresistive nanosensors, has been implemented for mutational analysis of CTCs enriched with the magnetic sifter. The use of these magnetic technologies, which are separate devices, may lead the way to routine preparation and characterization of "liquid biopsies" from cancer patients.

Development of a robust flow cytometry-based pharmacodynamic assay to detect phospho-protein signals for phosphatidylinositol 3-kinase inhibitors in multiple myeloma.

BACKGROUND: The phosphatidylinositol 3-kinase (PI3K) pathway plays an important role in multiple myeloma (MM), a blood cancer associated with uncontrolled proliferation of bone marrow plasma cells. This study aimed to develop a robust clinical pharmacodynamic (PD) assay to measure the on-target PD effects of the selective PI3K inhibitor GDC-0941 in MM patients. METHODS: We conducted an in vitro drug wash-out study to evaluate the feasibility of biochemical approaches in measuring the phosphorylation of S6 ribosomal protein (S6), one of the commonly used PD markers for PI3K pathway inhibition. We then developed a 7-color phospho-specific flow cytometry assay, or phospho flow assay, to measure the phosphorylation state of intracellular S6 in bone marrow aspirate (BMA) and peripheral blood (PB). Integrated mean fluorescence intensity (iMFI) was used to calculate fold changes of phosphorylation. Assay sensitivity was evaluated by comparing phospho flow with Meso Scale Discovery (MSD) and immunohistochemistry (IHC) assays. Finally, a sample handling method was developed to maintain the integrity of phospho signal during sample shipping and storage to ensure clinical application. RESULTS: The phospho flow assay provided single-cell PD monitoring of S6 phosphorylation in tumor and surrogate cells using fixed BMA and PB, assessing pathway modulation in response to GDC-0941 with sensitivity similar to that of MSD assay. The one-shot sample fixation and handling protocol herein demonstrated exceptional preservation of protein phosphorylation. In contrast, the IHC assay was less sensitive in terms of signal quantification while the biochemical approach (MSD) was less suitable to assess PD activities due to the undesirable impact associated with cell isolation on the protein phosphorylation in tumor cells. CONCLUSIONS: We developed a robust PD biomarker assay for the clinical evaluation of PI3K inhibitors in MM, allowing one to decipher the PD response in a relevant cell population. To our knowledge, this is the first report of an easily implemented clinical PD assay that incorporates an unbiased one-shot sample handling protocol, all (staining)-in-one (tube) phospho flow staining protocol, and an integrated modified data analysis for PD monitoring of kinase inhibitors in relevant cell populations in BMA and PB. The methods described here ensure a real-time, reliable and reproducible PD readout, which can provide information for dose selection as well as help to identify optimal combinations of targeted agents in early clinical trials.

Kif3a is necessary for initiation and maintenance of medulloblastoma.

Medulloblastoma (MB) cells arise from granule neuron precursors (GNPs) that have lost growth control. During normal development, GNPs divide in response to Sonic hedgehog (SHH), a ligand that binds to the patched (PTCH) receptor on GNPs. If one copy of the Ptch gene is lost, as in human Gorlin's syndrome and in Ptch(+/-) mice, MBs may form. Proper transduction of the SHH signal critically depends on primary cilia. Loss of primary cilia results in improper signal reception and failure to properly activate SHH target genes. KIF3a, part of a kinesin motor, is required for formation of primary cilia. Here, we use tamoxifen-induced ablation of Kif3a in GNPs of postnatal Ptch(+/-) mouse cerebella to show that KIF3a is necessary for MB formation. To investigate the importance of primary cilia in established tumors, we deleted Kif3a from cultured cells and from tumor cell grafts. The loss of Kif3a from established tumors led to their growth arrest and regression. MBs behave as if they are addicted to the presence of primary cilia. These results underscore the potential utility of agents that disrupt cilia for the treatment of Hh pathway-related MBs.

Learning from Jekyll to control Hyde: Hedgehog signaling in development and cancer.

The Hedgehog (Hh) cascade controls cell proliferation, differentiation and patterning of tissues during embryogenesis but is largely suppressed in the adult. The Hh pathway can become reactivated in cancer. Here, we assimilate data from recent studies to understand how and when the Hh pathway is turned on to aid the neoplastic process. Hh signaling is now known to have a role in established tumors, enabling categorization of tumors based on the role Hh signaling plays in their growth. This categorization has relevance for prognosis and targeted therapeutics. In the first category, abnormal Hh signaling initiates the tumor. In the second category, Hh signaling helps maintain the tumor. In the third category, Hh signaling is implicated but its role is not yet defined.

The output of Hedgehog signaling is controlled by the dynamic association between Suppressor of Fused and the Gli proteins.

The transcriptional program orchestrated by Hedgehog signaling depends on the Gli family of transcription factors. Gli proteins can be converted to either transcriptional activators or truncated transcriptional repressors. We show that the interaction between Gli3 and Suppressor of Fused (Sufu) regulates the formation of either repressor or activator forms of Gli3. In the absence of signaling, Sufu restrains Gli3 in the cytoplasm, promoting its processing into a repressor. Initiation of signaling triggers the dissociation of Sufu from Gli3. This event prevents formation of the repressor and instead allows Gli3 to enter the nucleus, where it is converted into a labile, differentially phosphorylated transcriptional activator. This key dissociation event depends on Kif3a, a kinesin motor required for the function of primary cilia. We propose that the Sufu-Gli3 interaction is a major control point in the Hedgehog pathway, a pathway that plays important roles in both development and cancer.

A NOD2-NALP1 complex mediates caspase-1-dependent IL-1beta secretion in response to Bacillus anthracis infection and muramyl dipeptide.

NOD2, a NOD-like receptor (NLR), is an intracellular sensor of bacterial muramyl dipeptide (MDP) that was suggested to promote secretion of the proinflammatory cytokine IL-1beta. Yet, the molecular mechanism by which NOD2 can stimulate IL-1beta secretion, and its biological significance were heretofore unknown. We found that NOD2 through its N-terminal caspase recruitment domain directly binds and activates caspase-1 to trigger IL-1beta processing and secretion in MDP-stimulated macrophages, whereas the C-terminal leucine-rich repeats of NOD2 prevent caspase-1 activation in nonstimulated cells. MDP challenge induces the association of NOD2 with another NLR protein, NALP1, and gel filtration analysis revealed the formation of a complex consisting of NOD2, NALP1, and caspase-1. Importantly, Bacillus anthracis infection induces IL-1beta secretion in a manner that depended on caspase-1 and NOD2. In vitro, Anthrax lethal toxin strongly potentiated IL-1beta secretion, and that response was NOD2 and caspase-1-dependent. Thus, NOD2 plays a key role in the B. anthracis-induced inflammatory response by being a critical mediator of IL-1beta secretion.