Discovery of GDC-0077 (Inavolisib), a Highly Selective Inhibitor and Degrader of Mutant PI3Kα

Small molecule inhibitors that target the phosphatidylinositol 3-kinase (PI3K) signaling pathway have received significant interest for the treatment of cancers. The class I isoform PI3Kα is most commonly associated with solid tumors via gene amplification or activating mutations. However, inhibitors demonstrating both PI3K isoform and mutant specificity have remained elusive. Herein, we describe the optimization and characterization of a series of benzoxazepin-oxazolidinone ATP-competitive inhibitors of PI3Kα which also induce the selective degradation of the mutant p110α protein, the catalytic subunit of PI3Kα. Structure-based design informed isoform-specific interactions within the binding site, leading to potent inhibitors with greater than 300-fold selectivity over the other Class I PI3K isoforms. Further optimization of pharmacokinetic properties led to excellent in vivo exposure and efficacy and the identification of clinical candidate GDC-0077 (inavolisib, 32), which is now under evaluation in a Phase III clinical trial as a treatment for patients with PIK3CA-mutant breast cancer.

Permanent pacemaker implantation in unexplained syncope patients with electrophysiology study-proven atrioventricular node disease

Funding Acknowledgements

Type of funding sources: None.

Background/Introduction: Syncope, whose cause is unknown after an initial assessment, has an uncertain prognosis. It is critical to identify patients at highest risk who may require a pacemaker and to identify the cause of recurrent syncope to prescribe proper therapy

Purpose

Aim of this study was to evaluate the effect of permanent pacing on the incidence of syncope in patients with unexplained syncope and electrophysiology study-proven atrioventricular node disease.

Methods

This was an observational study based on a prospective registry of 236 consecutive patients (60.20 ± 18.66 years, 63.1% male, 60.04 ± 9.50 bpm) presenting with recurrent unexplained syncope attacks admitted to our hospital for invasive electrophysiology study (EPS). Τhe implantation of a permanent antibradycardia pacemaker (ABP) was offered to all patients according to the results of the EPS. 135 patients received the ABP, while 101 denied.

Results

The mean of reported syncope episodes was 1.97 ± 1.10 (or presyncope 2.17 ± 1.50) before they were referred for a combined EP guided diagnostic and therapeutic approach. Over a mean follow-up of approximately 4 years (49.19 ±  29.58 months), the primary outcome event (syncope) occurred in 31 of 236 patients (13.1%), 6 of 135 (4.4%) in the ABP group as compared to 25 of 101 (24.8%) in the no pacemaker group (p < 0.001).

Conclusion

Among patients with a history of unexplained syncope, a set of positivity criteria for the presence of EPS defined atrioventricular node disease, identifies a subset of patients who will benefit from permanent pacing.

Noninvasive risk factors for the prediction of inducibility on programmed ventricular stimulation in post-MI patients with ejection fraction over 40% at SCD risk, insights from the PRESERVE EF study

Funding Acknowledgements

Type of funding sources: None.

Background

Sudden cardiac arrest (SCA) in post myocardial infarction (post-MI) patients with a relatively preserved left ventricular systolic function (LVEF≥40%) has an annual incidence of 1%, in the absence of adequate risk stratification methods and guideline recommendations for primary prevention. In the PRESERVE-EF study we used a two-step SCA risk stratification approach to detect patients at risk for major arrhythmic events. Seven noninvasive risk factors (NIRFs) were extracted from ambulatory electrocardiography (AECG). Patients with at least one NIRF present were referred for invasive programmed ventricular stimulation (PVS). Inducible patients received an ICD.

Purpose

To assess the performance of NIRFs extracted from 24hr AECG, based on the PRESERVE EF criteria, in predicting inducibility.

Methods

The PRESERVE EF study enrolled 575 patients. Two hundred and four of them had at least one NIRF and an indication for PVS, but 52 of them declined. Finally, 41 out of 152 patients who underwent PVS were inducible. For the present analysis data from these 152 patients (mean age 60 ± 10years, LVEF 49 ± 6%, 89% males) were analyzed. Chi-square test, univariate logistic regression and areas under ROC curves were calculated for the PVS inducibility endpoint.

Results

Age, male gender and LVEF for the PVS inducible patients group (n = 41) and the noninducible patients group (n = 111) were, respectively: 61 ± 9years vs 59 ± 10years (p = 0.310), 98% vs 86% (p = 0.048), 45 ± 4% vs 51 ± 7% (p < 0.001). Among NIRFs examined, LVEF ≤ 50%, nsVT≥1/24hour and presence of LPs on SAECG presented high and significant Odds Ratios (ORs) for a positive PVS study end point. A simple risk score based on cutoff points of LVEF ≤ 50%, NSVTepisode≥1/24hour and presence of LPs missed only 1 out of the 41 inducible patients and yielded: OR 14.146 (p = 0.01) with a high sensitivity 98% but low specificity 26% for a positive PVS (AUC = 0.65).

Conclusion

Cut off points of LVEF ≤ 50%, nsVTepisode≥1/24hour and presence of LPs were important predictors of inducibility. A simple risk score based on these predictors achieves high sensitivity but low specificity.  The final decision for an ICD implantation should be based on a positive PVS, which is irreplaceable in risk stratification.

Leadless pacing: First experience and outcomes in an isolated area in the setting of the Greek financial crisis

BACKGROUND

Leadless pacing (LP) is a novel permanent pacing modality without transvenous leads that is increasingly applied in certain circumstances. We aimed to report our preliminary experience in LP implementation.

CASE SERIES

This observational study represents a simple registry of LP systems implanted in our tertiary center from April 2018 until November 2019 in the setting of the Greek financial crisis. Consecutive patients from the isolated area of Northwestern Greece referred to our center for LP were included. Patients' clinical and procedural data, as well as follow-up events, were carefully recorded. Nine patients (mean age: 75 years; six men) were included and were followed for a median period of 20 months. The commonest indication for LP implantation was increased patient infection risk (n: seven), while in the remaining patients (n: two), the indication was problematic vein access along with concomitant comorbidities that increase infection risk. Most of the patients (6/9) were in sinus rhythm, while the rest had slow atrial fibrillation. During the follow-up period, two patients with end-stage renal disease suffered sudden cardiac death, two patients died due to pneumonia, and one patient died due to metastatic cancer. However, no device-related death occurred during the follow-up.

CONCLUSIONS

Our data indicate that LP's long-term cost-effectiveness is limited in patients with several comorbidities due to increased mortality. Indeed, considering its increased financial cost, well-defined patients' selection criteria should be developed and applied, especially in medium/low-income countries. HIPPOKRATIA 2021, 25 (2):75-78.

The effect of permanent pacemaker implantation following transcatheter aortic valve implantation upon survival

Purpose

Transcatheter aortic valve implantation (TAVI) is often followed by conduction abnormalities, leading to a permanent pacemaker implantation (PPI). Data regarding the clinical impact of PPI following TAVI is yet to be established.

Methods

Patients with severe and symptomatic aortic stenosis [effective orifice area (EOA) ≤1cm2] referred for TAVI at our institution were consecutively enrolled. Prospectively collected demographic, laboratory and echocardiographic data were retrospectively analyzed. Patients were stratified into two groups according to the need for PPI after TAVI and were followed up postoperatively with clinical and echocardiographic assessment. Primary clinical endpoint was all-cause mortality, as defined by the criteria proposed by the Valve Academic Research Consortium 2.

Results

In total, 292 patients were included (male: 50.2%, mean age: 80±7.6 years) in our study. Of these, 109 (37.5%) underwent PPI simultaneously or shortly after TAVI. The median follow-up period was 27.3 In this period, all-cause mortality showed no significant difference between patients with and those without PPI after TAVI (log-rank p=0.756), even after excluding patients with a pre-existing pacemaker from the analysis. Subgroup analysis also showed no difference in survival between patients with low ejection fraction (<50%) and those with preserved (≥50%) receiving a permanent pacemaker after TAVR (log-rank p=0.269). Taking into consideration factors that were found to associate to PPI in univariate analysis (pre TAVI - ejection fraction, pulmonary artery systolic pressure and New York Heart Association functional class) in a multivariate model, pre TAVI pulmonary artery systolic pressure was found to be an independent predictor of peri-procedural PPI [Exp(B): 0.977, 95% Confidence Interval: 0.957–0.998, B=−0.023, p=0.029]. Pre-TAVI conduction abnormalities and the degree of aortic annulus calcification, as assessed by computed-tomography, were not found to predict PPI after TAVI.

Conclusion

PPI following TAVI was not associated with survival at 27 months of follow-up, independently from the pre TAVI ejection fraction.

Figure 1

Funding Acknowledgement

Type of funding source: None

Arrhythmic risk stratification in heart failure mid-range ejection fraction patients with a non-invasive guiding to programmed ventricular stimulation two-step approach

Background

Although some post myocardial infarction (post-MI) and dilated cardiomyopathy (DCM) patients with mid-range ejection fraction heart failure (HFmrEF = 40–49%) face an increased risk for arrhythmic Sudden Cardiac Death (SCD), current guidelines do not recommend an implantable cardioverter-defibrillator (ICD).

Purpose

To assess the accuracy of a novel multifactorial two-step approach, with noninvasive risk factors (NIRFs) leading to programmed ventricular stimulation (PVS), for SCD risk stratification of hospitalized HFmrEF patients.

Methods

Forty-eight patients (male=83%, age = 64±14 years, LVEF = 45±5%, ischemic coronary disease = 69%) underwent a NIRF presence screening first step with ECG, SAECG, echocardiography and 24 hour ambulatory ECG (Holter). Thirty-two patients with presence of one out of three NIRFs (SAECG ≥2 positive criteria for late potentials, ventricular premature beats ≥240/24 hours, and ≥1 episode of non-sustained ventricular tachycardia on Holter) were further stratified with PVS. Patients were classified as either low (Group 1, n=16, NIRFs−), moderate (Group 2, n=18, NIRFs+ /PVS−) or high risk (Group 3, n=14, NIRFs+/PVS+). All Group 3 patients received an ICD.

Results

After 41±18 months, 9 out of 48 patients experienced the major arrhythmic event (MAE) endpoint (clinical ventricular tachycardia/fibrillation = 3, appropriate ICD activation = 6). The endpoint occurred more frequently in Group 3 (7/14, 50%) than in Groups 1 & 2 (2/34, 5.8%). A logistic regression model adjusted for PVS, age and LVEF revealed that PVS was an independent MAE predictor (OR: 21.152, 95% CI: 2.618–170.887, p=0.004). Kaplan Meier curves diverged significantly (p logrank <0.001) while PVS negative predictive value was 94%.

Conclusion

In hospitalized HFmrEF post-MI and DCM patients, a NIRFs leading to PVS two-step approach efficiently detected the subgroup at increased risk for MAEs.

Funding Acknowledgement

Type of funding source: None

Prevalence, pattern and associated cardiovascular risk of t-wave inversion in hypertensive patients: a 5-year follow-up study

Background

Data on prevalence and associated prognosis of repolarization abnormalities among hypertensive patients are limited.

Purpose

We investigated the presence and extent of ST-segment and T-wave changes in a hypertensive population and their predictive ability for cardiovascular disease.

Methods

We studied 1851 white Caucasian hypertensive patients (age 58±12 years, 51%females) without a history of cardiovascular disease for a mean period of 5.3±3.4 years. At the baseline examination, all patients underwent standard 12-lead electrocardiography. T-wave inversion (TWI) was defined as T-wave deflection ≥−0.1 mV in ≥2 contiguous leads,unless associated with bundle branch block. Anterior, lateral or inferior TWI was defined as TWIin leads V2-V4 or V5,V6, I, AVL or II, aVF respectively. Thedepth in millimeters of TWI in each lead was recorded and the maximum depth per location was calculated. ST depression was defined as ≥1mm in depth in two or more contiguous leads.During follow-up, patients underwent clinic visits at least yearly for management of hypertension and risk factors. The outcome studied was theincidence of cardiovascular morbidity set as the composite of non-fatal coronary artery disease and stroke.

Results

In the entire population, prevalence of TWI was 3.8%, of which 39% presented withanterior TWI, 73% withlateral TWI and 11% with inferior TWI. ST depression was observed in 3.6% of patients (anterior in 0.8%, inferior in 0.9% and lateral in 2.6%). Incidence of the composite endpoint during follow-up was 4%. Cox regression analysis revealed that presence of TWI was associated with a significantly greater risk for cardiovascular events (HR: 2.6, 95% CI: 1.1–5.9, p=0.025). The association was stronger for lateral TWI (HR: 3.3, 95%: CI: 1.34–8.30, p=0.01) compared to other locations. In multivariate models controlling for standard confounders these associations were overall sustained. Depth of TWI and presence of ST depression were not associated with cardiovascular risk.

Conclusions

Among hypertensive patients without cardiovascular disease, TWI is infrequent but significantly associated with future cardiovascular events.Lateral TWI carries the worse prognosis

Funding Acknowledgement

Type of funding source: None

Prognostic implication of electrocardiographic left ventricular strain in patients undergoing Transcatheter Aortic Valve Implantation

Background

Electrocardiographic (ECG) strain has been linked to excess cardiovascular morbidity and mortality in asymptomatic patients with aortic stenosis.

Purpose

We aim to determine the differential impact of baseline ECG-strain on long-term mortality after transcatheter aortic valve implantation (TAVI).

Methods

Patients with severe and symptomatic aortic stenosis (effective orifice area [EOA]≤1cm2), who were scheduled for TAVI with a self-expanding valve between May 2015 and May 2018 were consecutively enrolled. Left ventricular strain was defined as the presence of ≥1mm convex ST-segment depression with asymmetrical T-wave inversion in leads V5 to V6 on baseline ECG. Patients were excluded, if they had bundle branch block or a permanent pacemaker at baseline. Baseline parameters were compared, and multivariate Cox proportional hazard regression models were generated to assess outcome difference. The primary clinical endpoint was cumulative mortality defined according to the criteria proposed by the Valve Academic Research Consortium-2.

Results

Of the 171 patients screened, 56 patients were excluded due to left bundle branch block or paced rhythm. In the 115 included patients (mean age: 81.4±7), 36 patients (31.3%) had strain pattern on pre-TAVI ECG. There were no differences in baseline characteristics between the two groups. During a median follow-up of 2.32 years (IQR 1.62 to 3), 11 patients (9.6%) reached the primary clinical endpoint. Patients in the strain group had higher incidence of all-cause mortality compared to patients without left ventricular strain (25% vs 2.5%, χ2=14.4, p<0.001). Kaplan-Meier survival analysis showed a significantly decreased cumulative probability of survival at 3 years in patients with LV-strain compared with patients without LV-strain (log-rank p=0.002, Figure 1). In the multivariate analysis, left ventricular strain [Exp(B): 8.952, 95% Confidence Interval (CI): 1.215–65.938, B=2.192, p=0.031] and QRS duration [Exp(B): 1.058, 95% CI: 1.022–1.095, B=0.056, p<0.001] were found to be independent predictors of all-cause mortality after TAVI.

Conclusion

Baseline ECG left ventricular strain was an independent predictor of long-term mortality post TAVI. Systematic strain measurements might aid in risk-stratifying patients scheduled for TAVI.

Figure 1

Funding Acknowledgement

Type of funding source: None

Abstract PR03: Selective degradation of mutant PIK3CA promotes increased mutant specificity in a subset of PI3K ATP-competitive inhibitors

Activating mutations in PIK3CA are among the most significant oncogenic events across all cancers, making it an important target for drug development. Yet the application of PI3K inhibitors in the clinic has been limited by the difficulty of achieving an adequate therapeutic window, due to the critical role that PI3K signaling plays in normal physiologic processes, such as glucose homeostasis. In theory, the therapeutic window could be improved if it were possible to design mutant selective inhibitors, as has been demonstrated with other oncogenes such as EGFR. However, unlike EGFR, the most predominant PIK3CA activating mutations do not reside in the kinase active site, presenting a major challenge for rational structure-based design. Nevertheless, it was recently shown that the PI3K inhibitor taselisib is able to achieve modest levels of mutant selectivity both across cancer lines as well as in cell lines that were engineered to express mutant or wild-type PIK3CA. Taselisib was also shown to selectively induce degradation of mutant versus wild-type PIK3CA, leading to the speculation that this degradation may be responsible for the observed selectivity. In order to better understand the origins of mutant selectivity for taselisib and several other PIK3CA inhibitors, we assessed these inhibitors in a variety of biophysical and biochemical assays under conditions designed to mimic physiologic settings. In parallel, we also investigated the mechanistic basis of this selectivity in our engineered cell lines. Our results are consistent with the hypothesis that selective degradation of mutant PIK3CA is the predominant mechanism underlying mutant selectivity for this class of PIK3CA active site inhibitors.

This abstract is also being presented as Poster B03.

Citation Format: Lan Nguyen, Kyle Edgar, Kyung Song, Stephen Schmidt, Victorai Schutz, Noriko Ishisoko, Eric Torres, Akash Das, Divya Murali, Steve Sideris, Timothy Wendorff, Matt Saabye, Hans Purkey, Jawahar Sudhamsu, Steven Staben, Emily Hanan, Georgia Hatzivassiliou, Lori Friedman, Nicholas F. Endres. Selective degradation of mutant PIK3CA promotes increased mutant specificity in a subset of PI3K ATP-competitive inhibitors [abstract]. In: Proceedings of the AACR Special Conference on Targeting PI3K/mTOR Signaling; 2018 Nov 30-Dec 8; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(10_Suppl):Abstract nr PR03.

Targeting ferroptosis: A novel therapeutic strategy for the treatment of mitochondrial disease-related epilepsy

BACKGROUND

Mitochondrial disease is a family of genetic disorders characterized by defects in the generation and regulation of energy. Epilepsy is a common symptom of mitochondrial disease, and in the vast majority of cases, refractory to commonly used antiepileptic drugs. Ferroptosis is a recently-described form of iron- and lipid-dependent regulated cell death associated with glutathione depletion and production of lipid peroxides by lipoxygenase enzymes. Activation of the ferroptosis pathway has been implicated in a growing number of disorders, including epilepsy. Given that ferroptosis is regulated by balancing the activities of glutathione peroxidase-4 (GPX4) and 15-lipoxygenase (15-LO), targeting these enzymes may provide a rational therapeutic strategy to modulate seizure. The clinical-stage therapeutic vatiquinone (EPI-743, α-tocotrienol quinone) was reported to reduce seizure frequency and associated morbidity in children with the mitochondrial disorder pontocerebellar hypoplasia type 6. We sought to elucidate the molecular mechanism of EPI-743 and explore the potential of targeting 15-LO to treat additional mitochondrial disease-associated epilepsies.

METHODS

Primary fibroblasts and B-lymphocytes derived from patients with mitochondrial disease-associated epilepsy were cultured under standardized conditions. Ferroptosis was induced by treatment with the irreversible GPX4 inhibitor RSL3 or a combination of pharmacological glutathione depletion and excess iron. EPI-743 was co-administered and endpoints, including cell viability and 15-LO-dependent lipid oxidation, were measured.

RESULTS

EPI-743 potently prevented ferroptosis in patient cells representing five distinct pediatric disease syndromes with associated epilepsy. Cytoprotection was preceded by a dose-dependent decrease in general lipid oxidation and the specific 15-LO product 15-hydroxyeicosatetraenoic acid (15-HETE).

CONCLUSIONS

These findings support the continued clinical evaluation of EPI-743 as a therapeutic agent for PCH6 and other mitochondrial diseases with associated epilepsy.

Cell Active Hydroxylactam Inhibitors of Human Lactate Dehydrogenase with Oral Bioavailability in Mice

A series of trisubstituted hydroxylactams was identified as potent enzymatic and cellular inhibitors of human lactate dehydrogenase A. Utilizing structure-based design and physical property optimization, multiple inhibitors were discovered with <10 μM lactate IC₅₀ in a MiaPaca2 cell line. Optimization of the series led to 29, a potent cell active molecule (MiaPaca2 IC₅₀ = 0.67 μM) that also possessed good exposure when dosed orally to mice.

Role of corticosteroids in prostate cancer progression: implications for treatment strategy in metastatic castration-resistant patients

Corticosteroid agents (CA) are widely used in the treatment of metastatic castration-resistant prostate cancer (mCRPC) either as concomitant treatment with active agents such as docetaxel, cabazitaxel and abiraterone or in a palliative setting, predominantly due to their anti-inflammatory activity. However, the chronic use of CA has numerous side effects, especially in case of steroid-induced adrenal insufficiency. Furthermore, the latest clinical and preclinical data demonstrate that CA themselves are likely to promote tumour progression in certain populations of patients with mCRPC. Therefore, the role of CA in advanced disease should be carefully weighed for each patient and their withdrawal should be considered in some patients. This is necessary, especially in clinical trials that need good performance status patients to evaluate the activity and the safety of emerging drugs in mCRPC that do not require the concurrent use of CA. In oncology, there is no consensus on an algorithm of gradual steroid tapering and frequently the approach to this procedure is empirical. An algorithm is presented in this article based on clinical observations. Prospective studies are necessary to evaluate the efficacy and safety of the above-proposed algorithm in metastatic castration-resistant prostate cancer.

Discovery of Clinical Development Candidate GDC-0084, a Brain Penetrant Inhibitor of PI3K and mTOR

Inhibition of phosphoinositide 3-kinase (PI3K) signaling is an appealing approach to treat brain tumors, especially glioblastoma multiforme (GBM). We previously disclosed our successful approach to prospectively design potent and blood–brain barrier (BBB) penetrating PI3K inhibitors. The previously disclosed molecules were ultimately deemed not suitable for clinical development due to projected poor metabolic stability in humans. We, therefore, extended our studies to identify a BBB penetrating inhibitor of PI3K that was also projected to be metabolically stable in human. These efforts required identification of a distinct scaffold for PI3K inhibitors relative to our previous efforts and ultimately resulted in the identification of GDC-0084 (16). The discovery and preclinical characterization of this molecule are described within.

The Rational Design of Selective Benzoxazepin Inhibitors of the α-Isoform of Phosphoinositide 3-Kinase Culminating in the Identification of (S)-2-((2-(1-Isopropyl-1H-1,2,4-triazol-5-yl)-5,6-dihydrobenzo[f]imidazo[1,2-d][1,4]oxazepin-9-yl)oxy)propanamide (GDC-0326)

Inhibitors of the class I phosphoinositide 3-kinase (PI3K) isoform PI3Kα have received substantial attention for their potential use in cancer therapy. Despite the particular attraction of targeting PI3Kα, achieving selectivity for the inhibition of this isoform has proved challenging. Herein we report the discovery of inhibitors of PI3Kα that have selectivity over the other class I isoforms and all other kinases tested. In GDC-0032 (3, taselisib), we previously minimized inhibition of PI3Kβ relative to the other class I insoforms. Subsequently, we extended our efforts to identify PI3Kα-specific inhibitors using PI3Kα crystal structures to inform the design of benzoxazepin inhibitors with selectivity for PI3Kα through interactions with a nonconserved residue. Several molecules selective for PI3Kα relative to the other class I isoforms, as well as other kinases, were identified. Optimization of properties related to drug metabolism then culminated in the identification of the clinical candidate GDC-0326 (4).

Pyridones as Highly Selective, Noncovalent Inhibitors of T790M Double Mutants of EGFR

The rapid advancement of a series of noncovalent inhibitors of T790M mutants of EGFR is discussed. The optimization of pyridone 1, a nonselective high-throughput screening hit, to potent molecules with high levels of selectivity over wtEGFR and the broader kinome is described herein.

[Oncological intensive care: 2013 and 2014 years'review]

The objective of this paper is to review the literature published in 2013 and 2014 in the field of intensive care and emergency related to oncology. Are discussed because of new original publications: prognosis, life-supporting techniques, septic shock and infectious complications, anticancer treatment in intensive care, tumoral lysis syndrome, respiratory, thromboembolic and vascular, digestive and hepatic, and neurologic complications, oncologic emergencies, therapeutic limitations.

Noncovalent Mutant Selective Epidermal Growth Factor Receptor Inhibitors: A Lead Optimization Case Study

Because of their increased activity against activating mutants, first-generation epidermal growth factor receptor (EGFR) kinase inhibitors have had remarkable success in treating non-small-cell lung cancer (NSCLC) patients, but acquired resistance, through a secondary mutation of the gatekeeper residue, means that clinical responses only last for 8-14 months. Addressing this unmet medical need requires agents that can target both of the most common double mutants: T790M/L858R (TMLR) and T790M/del(746-750) (TMdel). Herein we describe how a noncovalent double mutant selective lead compound was optimized using a strategy focused on the structure-guided increase in potency without added lipophilicity or reduction of three-dimensional character. Following successive rounds of design and synthesis it was discovered that cis-fluoro substitution on 4-hydroxy- and 4-methoxypiperidinyl groups provided synergistic, substantial, and specific potency gain through direct interaction with the enzyme and/or effects on the proximal ligand oxygen atom. Further development of the fluorohydroxypiperidine series resulted in the identification of a pair of diastereomers that showed 50-fold enzyme and cell based selectivity for T790M mutants over wild-type EGFR (wtEGFR) in vitro and pathway knock-down in an in vivo xenograft model.

Androgen receptor expression in circulating tumour cells from castration-resistant prostate cancer patients treated with novel endocrine agents

Background:

Abiraterone and enzalutamide are novel endocrine treatments that abrogate androgen receptor (AR) signalling in castration-resistant prostate cancer (CRPC). Here, we developed a circulating tumour cells (CTCs)-based assay to evaluate AR expression in real-time in CRPC and investigated nuclear AR expression in CTCs in patients treated with enzalutamide and abiraterone.

Methods:

CTCs were captured and characterised using the CellSearch system. An automated algorithm to identify CTCs and quantify AR expression was employed. The primary aim was to evaluate the association between CTC AR expression and prior treatment with abiraterone or enzalutamide.

Results:

AR expression in CTCs was evaluated in 94 samples from 48 metastatic CRPC patients. We observed large intra-patient heterogeneity of AR expression in CTCs. Prior exposure to abiraterone or enzalutamide was not associated with a change in CTCs AR expression (median intensity and distribution of AR-positive classes). In support of this, we also confirmed maintained nuclear AR expression in tissue samples collected after progression on abiraterone. AR staining also identified additional AR-positive CD45-negative circulating cells that were CK-negative/weak and therefore missed using standard protocols. The number of these events correlated with traditional CTCs and was associated with worse outcome on univariate analysis.

Conclusions:

We developed a non-invasive method to monitor AR nuclear expression in CTCs. Our studies confirm nuclear AR expression in CRPC patients progressing on novel endocrine treatments. Owing to the significant heterogeneity of AR expression in CTCs, studies in larger cohorts of patients are required to identify associations with outcome.

Discovery of selective and noncovalent diaminopyrimidine-based inhibitors of epidermal growth factor receptor containing the T790M resistance mutation

Activating mutations within the epidermal growth factor receptor (EGFR) kinase domain, commonly L858R or deletions within exon 19, increase EGFR-driven cell proliferation and survival and are correlated with impressive responses to the EGFR inhibitors erlotinib and gefitinib in nonsmall cell lung cancer patients. Approximately 60% of acquired resistance to these agents is driven by a single secondary mutation within the EGFR kinase domain, specifically substitution of the gatekeeper residue threonine-790 with methionine (T790M). Due to dose-limiting toxicities associated with inhibition of wild-type EGFR (wtEGFR), we sought inhibitors of T790M-containing EGFR mutants with selectivity over wtEGFR. We describe the evolution of HTS hits derived from Jak2/Tyk2 inhibitors into selective EGFR inhibitors. X-ray crystal structures revealed two distinct binding modes and enabled the design of a selective series of novel diaminopyrimidine-based inhibitors with good potency against T790M-containing mutants of EGFR, high selectivity over wtEGFR, broad kinase selectivity, and desirable physicochemical properties.

Structure of the BRAF-MEK complex reveals a kinase activity independent role for BRAF in MAPK signaling

Numerous oncogenic mutations occur within the BRAF kinase domain (BRAF(KD)). Here we show that stable BRAF-MEK1 complexes are enriched in BRAF(WT) and KRAS mutant (MT) cells but not in BRAF(MT) cells. The crystal structure of the BRAF(KD) in a complex with MEK1 reveals a face-to-face dimer sensitive to MEK1 phosphorylation but insensitive to BRAF dimerization. Structure-guided studies reveal that oncogenic BRAF mutations function by bypassing the requirement for BRAF dimerization for activity or weakening the interaction with MEK1. Finally, we show that conformation-specific BRAF inhibitors can sequester a dormant BRAF-MEK1 complex resulting in pathway inhibition. Taken together, these findings reveal a regulatory role for BRAF in the MAPK pathway independent of its kinase activity but dependent on interaction with MEK.

Identification of 2-amino-5-aryl-pyrazines as inhibitors of human lactate dehydrogenase

A 2-amino-5-aryl-pyrazine was identified as an inhibitor of human lactate dehydrogenase A (LDHA) via a biochemical screening campaign. Biochemical and biophysical experiments demonstrated that the compound specifically interacted with human LDHA. Structural variation of the screening hit resulted in improvements in LDHA biochemical inhibition and pharmacokinetic properties. A crystal structure of an improved compound bound to human LDHA was also obtained and it explained many of the observed structure-activity relationships.

A hit to lead discovery of novel N-methylated imidazolo-, pyrrolo-, and pyrazolo-pyrimidines as potent and selective mTOR inhibitors

A series of N-7-methyl-imidazolopyrimidine inhibitors of the mTOR kinase have been designed and prepared, based on the hypothesis that the N-7-methyl substituent on imidazolopyrimidine would impart selectivity for mTOR over the related PI3Kα and δ kinases. The corresponding N-Me substituted pyrrolo[3,2-d]pyrimidines and pyrazolo[4,3-d]pyrimidines also show potent mTOR inhibition with selectivity toward both PI3α and δ kinases. The most potent compound synthesized is pyrazolo[4,3-d]pyrimidine 21c. Compound 21c shows a Ki of 2 nM against mTOR inhibition, remarkable selectivity (>2900×) over PI3 kinases, and excellent potency in cell-based assays.

Discovery of 2-{3-[2-(1-isopropyl-3-methyl-1H-1,2-4-triazol-5-yl)-5,6-dihydrobenzo[f]imidazo[1,2-d][1,4]oxazepin-9-yl]-1H-pyrazol-1-yl}-2-methylpropanamide (GDC-0032): a β-sparing phosphoinositide 3-kinase inhibitor with high unbound exposure and robust in vivo antitumor activity

Dysfunctional signaling through the phosphoinositide 3-kinase (PI3K)/AKT/mTOR pathway leads to uncontrolled tumor proliferation. In the course of the discovery of novel benzoxepin PI3K inhibitors, we observed a strong dependency of in vivo antitumor activity on the free-drug exposure. By lowering the intrinsic clearance, we derived a set of imidazobenzoxazepin compounds that showed improved unbound drug exposure and effectively suppressed growth of tumors in a mouse xenograft model at low drug dose levels. One of these compounds, GDC-0032 (11l), was progressed to clinical trials and is currently under phase I evaluation as a potential treatment for human malignancies.

Autoimmune haemolytic anaemia in a patient treated with capecitabine

A 61-year-old female, followed-up for a metastatic breast cancer, was admitted in our institution with conjunctival icterus, asthenia and abdominal crampoid pain. The patient was included in a clinical trial comparing the efficiency of capecitabine monotherapy versus capecitabine conjugated with a new biological agent in a randomised and double blind trial. The patient was in the capecitabine alone arm. Biological tests performed upon admission suggested the diagnosis of haemolytic anaemia. Moreover, the direct Coombs test result was twice positive indicating autoimmune haemolytic anaemia. Capecitabine has been reported to cause haemolysis either alone or combined with lapatinib, each time with a mechanism other than immunological. In this clinical case, capecitabine is the most likely factor causing an autoimmune haemolytic anaemia.