Maternity care for refugees living in Greek refugee camps: What are the challenges to provision?

BACKGROUND: Over a two-year period between 2015 and 2016, unprecedented numbers of people arrived in Greece fleeing conflict, persecution, and poverty. With new arrivals every day, there is a significant unmet need for health care provision, posing a challenge to the Greek Healthcare System. For pregnant refugees, a known vulnerable group, this has resulted in a complex partnership of shared maternity care between humanitarian organizations, the Greek national health care system, and European multi-state initiatives. Our aim was to understand the challenges to providing maternity care services in Greek refugee camps as perceived by health care providers. METHODS: A qualitative study comprising observation and semi-structured interviews with health care providers working with pregnant refugees was conducted in five refugee camps in May 2017. Interviews were transcribed and analyzed with thematic coding. RESULTS: Twenty-one health care providers were interviewed and field notes taken from observational study of services in five refugee camps. Health care providers describe difficult cross-cultural communication to be their biggest challenge to caring for pregnant refugee women. The limited availability of female only safe spaces is also identified as a barrier. Lastly, the overburdened Greek public health system limits their ability to provide care. CONCLUSIONS: Our research supports other literature describing difficult communication and the overburdened Greek health system as significant health care barriers for pregnant refugees in Greece. There is limited literature examining the role of "safe space," and further research is needed. Stakeholders providing maternity care to refugees should look to tackle these key issues as they seek to provide care to this population.

Emergence of resistance to tyrosine kinase inhibitors in non-small-cell lung cancer can be delayed by an upfront combination with the HSP90 inhibitor onalespib.

BACKGROUND: Tyrosine kinase inhibitors, such as crizotinib and erlotinib, are widely used to treat non-small-cell lung cancer, but after initial response, relapse is common because of the emergence of resistance through multiple mechanisms. Here, we investigated whether a frontline combination with an HSP90 inhibitor could delay the emergence of resistance to these inhibitors in preclinical lung cancer models. METHODS: The HSP90 inhibitor, onalespib, was combined with either crizotinib or erlotinib in ALK- or EGFR-activated xenograft models respectively (H2228, HCC827). RESULTS: In both models, after initial response to the monotherapy kinase inhibitors, tumour relapse was observed. In contrast, tumour growth remained inhibited when treated with an onalespib/kinase inhibitor combination. Analysis of H2228 tumours, which had relapsed on crizotinib monotherapy, identified a number of clinically relevant crizotinib resistance mechanisms, suggesting that HSP90 inhibitor treatment was capable of suppressing multiple mechanisms of resistance. Resistant cell lines, derived from these tumours, retained sensitivity to onalespib (proliferation and signalling pathways were inhibited), indicating that, despite their resistance to crizotinib, they were still sensitive to HSP90 inhibition. CONCLUSIONS: Together, these preclinical data suggest that frontline combination with an HSP90 inhibitor may be a method for delaying the emergence of resistance to targeted therapies.

The impact of dasatinib on pregnancy outcomes.

Prolonged survival in patients with chronic myeloid leukemia treated with BCR-ABL1-targeted tyrosine kinase inhibitors allows consideration of parenthood for patients on chronic therapy, but there are limited data about the effects of dasatinib on pregnancy. Pregnancy-related outcomes in dasatinib-treated patients or their partners reported to Bristol-Myers Squibb from clinical trials or healthcare providers through December 2013 were reviewed. Outcomes were available in 46/78 dasatinib-treated women (59%) and 33/69 partners of dasatinib-treated men (48%). Fifteen women (33%) delivered a normal infant; 18 (39%) and 8 (17%) had an elective or spontaneous abortion; and 5 (11%) had an abnormal pregnancy. There were 7 reports of fetal/infant abnormalities (encephalocele, renal tract abnormalities, and hydrops fetalis). Thirty of 33 (91%) infants fathered by dasatinib-treated men were reported normal at birth. Also, animal studies evaluated the impact of dasatinib on fertility, embryo-fetal toxicity, and development, suggesting that dasatinib may be a selective developmental toxicant. The outcomes of most pregnancies conceived by men treated with dasatinib were normal, but due to the small number of cases, further monitoring is required. Significant effects on pregnancy outcomes in women treated with dasatinib were found, supporting current recommendations that women avoid becoming pregnant during dasatinib treatment and be informed of fetal risks.

Cardiovascular and pulmonary adverse events in patients treated with BCR-ABL inhibitors: Data from the FDA Adverse Event Reporting System.

Rare but serious cardiovascular and pulmonary adverse events (AEs) have been reported in patients with chronic myeloid leukemia treated with BCR-ABL inhibitors. Clinical trial data may not reflect the full AE profile of BCR-ABL inhibitors because of stringent study entry criteria, relatively small sample size, and limited duration of follow-up. To determine the utility of the FDA AE Reporting System (FAERS) surveillance database for identifying AEs possibly associated with the BCR-ABL inhibitors imatinib, dasatinib, and nilotinib in the postmarketing patient population, we conducted Multi-Item Gamma Poisson Shrinker disproportionality analyses of FAERS reports on AEs in relevant system organ classes. Signals consistent with the known safety profiles of these agents as well as signals for less well-described AEs were detected. Bone marrow necrosis, conjunctival hemorrhage, and peritoneal fluid retention events were uniquely associated with imatinib. AEs that most commonly reached the threshold for dasatinib consisted of terms relating to hemorrhage and fluid retention, including pleural effusion and pericardial effusion. Most terms that reached the threshold solely with nilotinib were related to peripheral and cardiac vascular events. Although this type of analysis cannot determine AE incidence or establish causality, these findings elucidate the AEs reported in patients treated with BCR-ABL inhibitors across multiple clinical trials and in the community setting for all approved and nonapproved indications, suggesting drug-AE associations warrant further investigation. These findings emphasize the need to consider patient comorbidities when selecting amongst BCR-ABL inhibitors.

Clinical features of pulmonary arterial hypertension in patients receiving dasatinib.

The prognosis of most leukemia patients treated with BCR-ABL tyrosine kinase inhibitors (TKIs) is favorable, and a more precise understanding of serious and potentially irreversible treatment-related toxicities is essential to properly inform treatment choice. Few cases of pulmonary arterial hypertension (PAH) have been reported in patients with leukemia treated with dasatinib, a second-generation BCR-ABL TKI. To better understand characteristics and outcomes of dasatinib-treated patients with PAH, all clinical cases of PAH confirmed by right-heart catheterization in the Bristol-Myers Squibb pharmacovigilance database (N = 41), including 22 previously unpublished cases, were examined for previous treatments for leukemia, patient characteristics, time to PAH onset, and outcomes. Our analysis shows that compared with PAH due to other etiologies, dasatinib-related PAH is atypical, in that it is associated with partial to complete reversibility upon treatment discontinuation. The incidence of dasatinib-related PAH appears to be low. Most PAH cases were observed in patients who had received prior treatments for leukemia. No specific patient attributes appear to be associated with an increased risk of developing PAH while receiving dasatinib. Symptoms of PAH in dasatinib-treated leukemia patients should prompt a thorough workup, including consideration of confirmatory right-heart catheterization. In cases of confirmed PAH, dasatinib should be discontinued.

Fragment-Based Discovery of a Series of Allosteric-Binding Site Modulators of ß-Glucocerebrosidase.

ß-Glucocerebrosidase (GBA/GCase) mutations leading to misfolded protein cause Gaucher's disease and are a major genetic risk factor for Parkinson's disease and dementia with Lewy bodies. The identification of small molecule pharmacological chaperones that can stabilize the misfolded protein and increase delivery of degradation-prone mutant GCase to the lysosome is a strategy under active investigation. Here, we describe the first use of fragment-based drug discovery (FBDD) to identify pharmacological chaperones of GCase. The fragment hits were identified by using X-ray crystallography and biophysical techniques. This work led to the discovery of a series of compounds that bind GCase with nM potency and positively modulate GCase activity in cells.

Fragment-Based Discovery of Allosteric Inhibitors of SH2 Domain-Containing Protein Tyrosine Phosphatase-2 (SHP2).

The ubiquitously expressed protein tyrosine phosphatase SHP2 is required for signaling downstream of receptor tyrosine kinases (RTKs) and plays a role in regulating many cellular processes. Genetic knockdown and pharmacological inhibition of SHP2 suppresses RAS/MAPK signaling and inhibit the proliferation of RTK-driven cancer cell lines. Here, we describe the first reported fragment-to-lead campaign against SHP2, where X-ray crystallography and biophysical techniques were used to identify fragments binding to multiple sites on SHP2. Structure-guided optimization, including several computational methods, led to the discovery of two structurally distinct series of SHP2 inhibitors binding to the previously reported allosteric tunnel binding site (Tunnel Site). One of these series was advanced to a low-nanomolar lead that inhibited tumor growth when dosed orally to mice bearing HCC827 xenografts. Furthermore, a third series of SHP2 inhibitors was discovered binding to a previously unreported site, lying at the interface of the C-terminal SH2 and catalytic domains.

A real-world study to assess the association of cardiovascular adverse events (CVAEs) with ibrutinib as first-line (1L) treatment for patients with chronic lymphocytic leukaemia (CLL) in the United States.

Ibrutinib, a Bruton's tyrosine kinase inhibitor, is often used as first-line (1L) treatment of chronic lymphocytic leukaemia (CLL); however, it is associated with an increased risk for cardiovascular adverse events (CVAEs). This real-world study adds to existing literature by simultaneously investigating the correlation between pre-existing CV risk factors and the relative cardiotoxicity of ibrutinib vs other therapies in CLL/small lymphocytic lymphoma (SLL). Using a real-world database, the risk of subsequent CVAEs (any CVAE, atrial fibrillation [AF], or hypertension) were compared among patients who received 1L ibrutinib monotherapy or another type of non-ibrutinib therapy, grouped as intensive (IT) or non-intensive therapy (NIT). Each patient's baseline CV risk was estimated using the Framingham risk score. Inverse probability treatment weighting was incorporated into a logistic regression model to reduce baseline imbalance. Results showed ibrutinib was significantly associated with higher risk of CVAEs regardless of baseline CV risk. Compared with IT, odds ratios of any CVAE, hypertension, or AF were 2.61, 3.66, and 3.02, respectively vs 1.88, 2.13, and 2.46, respectively, with NIT. Sensitivity analyses confirmed the findings were robust. These results suggest clinical caution should be taken when selecting ibrutinib for patients with CLL/SLL, especially in those with high baseline CV risk.

The heat shock protein 90 inhibitor, AT13387, displays a long duration of action in vitro and in vivo in non-small cell lung cancer.

A ubiquitously expressed chaperone, heat shock protein 90 (HSP90) is of considerable interest as an oncology target because tumor cells and oncogenic proteins are acutely dependent on its activity. AT13387 (2,4-dihydroxy-5-isopropyl-phenyl)-[5-(4-methyl-piperazin-1-ylmethyl)-1,3-dihydro-isoindol-2-yl] methanone, l-lactic acid salt) a novel, high-affinity HSP90 inhibitor, which is currently being clinically tested, has shown activity against a wide array of tumor cell lines, including lung cancer cell lines. This inhibitor has induced the degradation of specific HSP90 client proteins for up to 7 days in tumor cell lines in vitro. The primary driver of cell growth (mutant epidermal growth factor receptors) was particularly sensitive to HSP90 inhibition. The long duration of client protein knockdown and suppression of phospho-signaling seen in vitro after treatment with AT13387 was also apparent in vivo, with client proteins and phospho-signaling suppressed for up to 72 h in xenograft tumors after treatment with a single dose of AT13387. Pharmacokinetic analyses indicated that while AT13387 was rapidly cleared from blood, its retention in tumor xenografts was markedly extended, and it was efficacious in a range of xenograft models. AT13387's long duration of action enabled, in particular, its efficacious once weekly administration in human lung carcinoma xenografts. The use of longer-acting HSP90 inhibitors, such as AT13387, on less frequent dosing regimens has the potential to maintain antitumor efficacy as well as minimize systemic exposure and unwanted effects on normal tissues.

ASTX029, a Novel Dual-mechanism ERK Inhibitor, Modulates Both the Phosphorylation and Catalytic Activity of ERK.

The MAPK signaling pathway is commonly upregulated in human cancers. As the primary downstream effector of the MAPK pathway, ERK is an attractive therapeutic target for the treatment of MAPK-activated cancers and for overcoming resistance to upstream inhibition. ASTX029 is a highly potent and selective dual-mechanism ERK inhibitor, discovered using fragment-based drug design. Because of its distinctive ERK-binding mode, ASTX029 inhibits both ERK catalytic activity and the phosphorylation of ERK itself by MEK, despite not directly inhibiting MEK activity. This dual mechanism was demonstrated in cell-free systems, as well as cell lines and xenograft tumor tissue, where the phosphorylation of both ERK and its substrate, ribosomal S6 kinase (RSK), were modulated on treatment with ASTX029. Markers of sensitivity were highlighted in a large cell panel, where ASTX029 preferentially inhibited the proliferation of MAPK-activated cell lines, including those with BRAF or RAS mutations. In vivo, significant antitumor activity was observed in MAPK-activated tumor xenograft models following oral treatment. ASTX029 also demonstrated activity in both in vitro and in vivo models of acquired resistance to MAPK pathway inhibitors. Overall, these findings highlight the therapeutic potential of a dual-mechanism ERK inhibitor such as ASTX029 for the treatment of MAPK-activated cancers, including those which have acquired resistance to inhibitors of upstream components of the MAPK pathway. ASTX029 is currently being evaluated in a first in human phase I-II clinical trial in patients with advanced solid tumors (NCT03520075).

Discovery of ASTX029, A Clinical Candidate Which Modulates the Phosphorylation and Catalytic Activity of ERK1/2.

Aberrant activation of the mitogen-activated protein kinase pathway frequently drives tumor growth, and the ERK1/2 kinases are positioned at a key node in this pathway, making them important targets for therapeutic intervention. Recently, a number of ERK1/2 inhibitors have been advanced to investigational clinical trials in patients with activating mutations in B-Raf proto-oncogene or Ras. Here, we describe the discovery of the clinical candidate ASTX029 (15) through structure-guided optimization of our previously published isoindolinone lead (7). The medicinal chemistry campaign focused on addressing CYP3A4-mediated metabolism and maintaining favorable physicochemical properties. These efforts led to the identification of ASTX029, which showed the desired pharmacological profile combining ERK1/2 inhibition with suppression of phospho-ERK1/2 (pERK) levels, and in addition, it possesses suitable preclinical pharmacokinetic properties predictive of once daily dosing in humans. ASTX029 is currently in a phase I-II clinical trial in patients with advanced solid tumors.

AT9283, a potent inhibitor of the Aurora kinases and Jak2, has therapeutic potential in myeloproliferative disorders.

Constitutive activation of Janus kinase (Jak) 2 is the most prevalent pathogenic event observed in the myeloproliferative disorders (MPD), suggesting that inhibitors of Jak2 may prove valuable in their management. Inhibition of the Aurora kinases has also proven to be an effective therapeutic strategy in a number of haematological malignancies. AT9283 is a multi-targeted kinase inhibitor with potent activity against Jak2 and Aurora kinases A and B, and is currently being evaluated in clinical trials. To investigate the therapeutic potential of AT9283 in the MPD we studied its activity in a number of Jak2-dependent systems. AT9283 potently inhibited proliferation and Jak2-related signalling in Jak2-dependent cell lines as well as inhibiting the formation of erythroid colonies from haematopoietic progenitors isolated from MPD patients with Jak2 mutations. The compound also demonstrated significant therapeutic potential in vivo in an ETV6-JAK2 (TEL-JAK2) murine leukaemia model. Inhibition of both Jak2 and Aurora B was observed in the model systems used, indicating a dual mechanism of action. Our results suggest that AT9283 may be a valuable therapy in patients with MPD and that the dual inhibition of Jak2 and the Aurora kinases may potentially offer combinatorial efficacy in the treatment of these diseases.

Biological characterization of AT7519, a small-molecule inhibitor of cyclin-dependent kinases, in human tumor cell lines.

Cyclin-dependent kinases (CDK), and their regulatory cyclin partners, play a central role in eukaryotic cell growth, division, and death. This key role in cell cycle progression, as well as their deregulation in several human cancers, makes them attractive therapeutic targets in oncology. A series of CDK inhibitors was developed using Astex's fragment-based medicinal chemistry approach, linked to high-throughput X-ray crystallography. A compound from this series, designated AT7519, is currently in early-phase clinical development. We describe here the biological characterization of AT7519, a potent inhibitor of several CDK family members. AT7519 showed potent antiproliferative activity (40-940 nmol/L) in a panel of human tumor cell lines, and the mechanism of action was shown here to be consistent with the inhibition of CDK1 and CDK2 in solid tumor cell lines. AT7519 caused cell cycle arrest followed by apoptosis in human tumor cells and inhibited tumor growth in human tumor xenograft models. Tumor regression was observed following twice daily dosing of AT7519 in the HCT116 and HT29 colon cancer xenograft models. We show that these biological effects are linked to inhibition of CDKs in vivo and that AT7519 induces tumor cell apoptosis in these xenograft models. AT7519 has an attractive biological profile for development as a clinical candidate, and the tolerability and efficacy in animal models compare favorably with other CDK inhibitors in clinical development. Studies described here formed the biological rationale for investigating the potential therapeutic benefit of AT7519 in cancer patients.

Fragment-based discovery of mexiletine derivatives as orally bioavailable inhibitors of urokinase-type plasminogen activator.

Fragment-based lead discovery has been applied to urokinase-type plasminogen activator (uPA). The (R)-enantiomer of the orally active drug mexiletine 5 (a fragment hit from X-ray crystallographic screening) was the chemical starting point. Structure-aided design led to elaborated inhibitors that retained the key interactions of (R)-5 while gaining extra potency by simultaneously occupying neighboring regions of the active site. Subsequent optimization led to 15, a potent, selective, and orally bioavailable inhibitor of uPA.

ASTX660, a Novel Non-peptidomimetic Antagonist of cIAP1/2 and XIAP, Potently Induces TNFα-Dependent Apoptosis in Cancer Cell Lines and Inhibits Tumor Growth.

Because of their roles in the evasion of apoptosis, inhibitor of apoptosis proteins (IAP) are considered attractive targets for anticancer therapy. Antagonists of these proteins have the potential to switch prosurvival signaling pathways in cancer cells toward cell death. Various SMAC-peptidomimetics with inherent cIAP selectivity have been tested clinically and demonstrated minimal single-agent efficacy. ASTX660 is a potent, non-peptidomimetic antagonist of cIAP1/2 and XIAP, discovered using fragment-based drug design. The antagonism of XIAP and cIAP1 by ASTX660 was demonstrated on purified proteins, cells, and in vivo in xenograft models. The compound binds to the isolated BIR3 domains of both XIAP and cIAP1 with nanomolar potencies. In cells and xenograft tissue, direct antagonism of XIAP was demonstrated by measuring its displacement from caspase-9 or SMAC. Compound-induced proteasomal degradation of cIAP1 and 2, resulting in downstream effects of NIK stabilization and activation of noncanonical NF-κB signaling, demonstrated cIAP1/2 antagonism. Treatment with ASTX660 led to TNFα-dependent induction of apoptosis in various cancer cell lines in vitro, whereas dosing in mice bearing breast and melanoma tumor xenografts inhibited tumor growth. ASTX660 is currently being tested in a phase I-II clinical trial (NCT02503423), and we propose that its antagonism of cIAP1/2 and XIAP may offer improved efficacy over first-generation antagonists that are more cIAP1/2 selective. Mol Cancer Ther; 17(7); 1381-91. ©2018 AACR.

Fragment-Based Discovery of a Potent, Orally Bioavailable Inhibitor That Modulates the Phosphorylation and Catalytic Activity of ERK1/2.

Aberrant activation of the MAPK pathway drives cell proliferation in multiple cancers. Inhibitors of BRAF and MEK kinases are approved for the treatment of BRAF mutant melanoma, but resistance frequently emerges, often mediated by increased signaling through ERK1/2. Here, we describe the fragment-based generation of ERK1/2 inhibitors that block catalytic phosphorylation of downstream substrates such as RSK but also modulate phosphorylation of ERK1/2 by MEK without directly inhibiting MEK. X-ray crystallographic and biophysical fragment screening followed by structure-guided optimization and growth from the hinge into a pocket proximal to the C-α helix afforded highly potent ERK1/2 inhibitors with excellent kinome selectivity. In BRAF mutant cells, the lead compound suppresses pRSK and pERK levels and inhibits proliferation at low nanomolar concentrations. The lead exhibits tumor regression upon oral dosing in BRAF mutant xenograft models, providing a promising basis for further optimization toward clinical pERK1/2 modulating ERK1/2 inhibitors.

Application of fragment screening by X-ray crystallography to beta-secretase.

This paper describes an application of fragment screening to the aspartyl protease enzyme, beta-secretase (BACE-1), using high throughput X-ray crystallography. Three distinct chemotypes were identified by X-ray crystallography as binding to the catalytic aspartates either via an aminoheterocycle (such as 2-aminoquinoline), a piperidine, or an aliphatic hydroxyl group. The fragment hits were weak inhibitors of BACE-1 in the millimolar range but were of interest because most of them displayed relatively good ligand efficiencies. The aminoheterocycles exhibited a novel recognition motif that has not been seen before with aspartic proteases. Virtual screening around this motif identified an aminopyridine with increased potency and attractive growth points for further elaboration using structure-based drug design. The companion paper illustrates how sub-micromolar inhibitors were developed starting from this fragment.

Application of fragment screening by X-ray crystallography to the discovery of aminopyridines as inhibitors of beta-secretase.

Fragment-based lead discovery has been successfully applied to the aspartyl protease enzyme beta-secretase (BACE-1). Fragment hits that contained an aminopyridine motif binding to the two catalytic aspartic acid residues in the active site of the enzyme were the chemical starting points. Structure-based design approaches have led to identification of low micromolar lead compounds that retain these interactions and additionally occupy adjacent hydrophobic pockets of the active site. These leads form two subseries, for which compounds 4 (IC50 = 25 microM) and 6c (IC50 = 24 microM) are representative. In the latter series, further optimization has led to 8a (IC50 = 690 nM).

In vitro and in vivo evaluation of dasatinib and imatinib on physiological parameters of pulmonary arterial hypertension.

PURPOSE: Pulmonary arterial hypertension (PAH) results from occlusion or vasoconstriction of pulmonary vessels, leading to progressive right ventricular failure. Dasatinib, a BCR-ABL1 tyrosine kinase inhibitor (TKI) approved for the treatment of chronic myelogenous leukemia, has been associated with PAH. In contrast, the BCR-ABL1 TKI imatinib has demonstrated anti-vasoproliferative properties and has been investigated as a potential treatment for PAH. Here we describe studies evaluating the effects of dasatinib and imatinib on cardiovascular and pulmonary functions to understand the reported differential consequences of the two TKIs in a clinical setting. METHODS: The direct effects of dasatinib and imatinib were explored in vivo to investigate possible mechanisms of dasatinib-induced PAH. In addition, effects of dasatinib and imatinib on PAH-related mediators were evaluated in vitro. RESULTS: In rats, both TKIs increased plasma nitric oxide (NO), did not induce PAH-related structural or molecular changes in PA or lungs, and did not alter hemodynamic lung function compared with positive controls. Similarly, in the pulmonary artery endothelial cells and smooth muscle cells co-culture model, imatinib and dasatinib increased NO and decreased endothelin-1 protein and mRNA. CONCLUSIONS: The results of these studies indicated that dasatinib did not induce physiological changes or molecular signatures consistent with PAH when compared to positive controls. Instead, dasatinib induced changes consistent with imatinib. Both dasatinib and imatinib induced biochemical and structural changes consistent with a protective effect for PAH. These data suggest that other factors of unclear etiology contributed to the development of PAH in patients treated with dasatinib.

Second-Generation HSP90 Inhibitor Onalespib Blocks mRNA Splicing of Androgen Receptor Variant 7 in Prostate Cancer Cells.

Resistance to available hormone therapies in prostate cancer has been associated with alternative splicing of androgen receptor (AR) and specifically, the expression of truncated and constitutively active AR variant 7 (AR-V7). The transcriptional activity of steroid receptors, including AR, is dependent on interactions with the HSP90 chaperone machinery, but it is unclear whether HSP90 modulates the activity or expression of AR variants. Here, we investigated the effects of HSP90 inhibition on AR-V7 in prostate cancer cell lines endogenously expressing this variant. We demonstrate that AR-V7 and full-length AR (AR-FL) were depleted upon inhibition of HSP90. However, the mechanisms underlying AR-V7 depletion differed from those for AR-FL. Whereas HSP90 inhibition destabilized AR-FL and induced its proteasomal degradation, AR-V7 protein exhibited higher stability than AR-FL and did not require HSP90 chaperone activity. Instead, HSP90 inhibition resulted in the reduction of AR-V7 mRNA levels but did not affect total AR transcript levels, indicating that HSP90 inhibition disrupted AR-V7 splicing. Bioinformatic analyses of transcriptome-wide RNA sequencing data confirmed that the second-generation HSP90 inhibitor onalespib altered the splicing of at least 557 genes in prostate cancer cells, including AR. These findings indicate that the effects of HSP90 inhibition on mRNA splicing may prove beneficial in prostate cancers expressing AR-V7, supporting further clinical investigation of HSP90 inhibitors in malignancies no longer responsive to androgen deprivation. Cancer Res; 76(9); 2731-42. ©2016 AACR.