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1.
Future Oncol ; : 1-8, 2024 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-38861293

RESUMO

Treatment options for patients with biliary tract cancer are limited, and the prognosis is poor. CTX-009, a novel bispecific antibody targeting both DLL4 and VEGF-A, has demonstrated antitumor activity in patients with advanced cancers as both a monotherapy and in combination with chemotherapy. In a phase II study of patients with advanced biliary tract cancer who had received one or two prior therapies, CTX-009 with paclitaxel demonstrated a 37.5% overall response rate (ORR). Described here is the design of and rationale for COMPANION-002, a randomized phase II/III study, which will evaluate the safety and efficacy of CTX-009 in combination with paclitaxel versus paclitaxel alone as second-line treatment for patients with advanced biliary tract cancer. The primary end point is ORR, and crossover is allowed.Clinical Trial Registration: NCT05506943 (ClinicalTrials.gov).


Looking for new options for patients with advanced biliary tract cancer? Explore COMPANION-002, Compass Therapeutics' phase II/III study of CTX-009 + paclitaxel as a second line treatment.#CMPX #biotech #healthcare #rarecancer.

2.
EClinicalMedicine ; 58: 101917, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-37090438

RESUMO

Background: Anti-programmed cell death protein 1 antibodies plus multikinase inhibitors have shown encouraging activity in several tumour types, including colorectal cancer. This study assessed regorafenib plus nivolumab in patients with microsatellite stable/mismatch repair-proficient metastatic colorectal cancer. Methods: This single-arm, open-label, multicentre phase 2 study enrolled adults from 13 sites in the USA with previously treated advanced microsatellite stable/mismatch repair-proficient metastatic colorectal cancer. Eligible patients had known extended RAS and BRAF status, progression or intolerance to no more than two (for extended RAS mutant) or three (for extended RAS wild type) lines of systemic chemotherapy and an Eastern Cooperative Oncology Group performance status of 0 or 1. Regorafenib 80 mg/day was administered orally for 3 weeks on/1 week off (increased to 120 mg/day if 80 mg/day was well tolerated) with intravenous nivolumab 480 mg every 4 weeks. Primary endpoint was objective response rate. Secondary endpoints included safety, overall survival, and progression-free survival. Exploratory endpoints included biomarkers associated with antitumour activity. Patients who received at least one dose of study intervention were included in the efficacy and safety analyses. Tumour assessments were carried out every 8 weeks for the first year, and every 12 weeks thereafter until progressive disease/end of the study, and objective response rate was analysed after all patients had met the criteria for primary completion of five post-baseline scans and either 10-months' follow-up or drop out. This trial is registered with ClinicalTrials.gov, number NCT04126733. Findings: Between 14 October 2019 and 14 January 2020, 94 patients were enrolled, 70 received treatment. Five patients had a partial response, yielding an objective response rate of 7% (95% CI 2.4-15.9; p = 0.27). All responders had no liver metastases at baseline. Median overall survival (data immature) and progression-free survival were 11.9 months (95% CI 7.0-not evaluable) and 1.8 months (95% CI 1.8-2.4), respectively. Most patients (97%, 68/70) experienced a treatment-related adverse event; 51% were grade 1 or 2, 40% were grade 3, 3% were grade 4, and 3% were grade 5. The most common (≥20%) events were fatigue (26/70), palmar-plantar erythrodysesthesia syndrome (19/70), maculopapular rash (17/70), increased blood bilirubin (14/70), and decreased appetite (14/70). Higher baseline expression of tumour biomarkers of immune sensitivity correlated with antitumour activity. Interpretation: Further studies are warranted to identify subgroups of patients with clinical characteristics or biomarkers that would benefit most from treatment with regorafenib plus nivolumab. Funding: Bayer/Bristol Myers Squibb.

3.
Cancer Med ; 12(4): 4195-4205, 2023 02.
Artigo em Inglês | MEDLINE | ID: mdl-36263922

RESUMO

BACKGROUND: Limited data are available regarding second-line (2 L) treatment for advanced or metastatic biliary tract cancers (BTC) in the US real-world setting. This study explores the rapidly evolving and growing treatment landscape in the 2 L setting for advanced or metastatic BTC with a large cohort of patients treated in a community oncology setting. METHODS: Adult patients with BTC initiating 2 L treatment after a platinum-containing first-line between 1/1/10- and 6/30/19 were identified from the US Oncology Network electronic healthcare record database and followed through 12/31/19. Baseline patient and treatment characteristics were analyzed descriptively, including overall response rate (ORR) in the real-world clinical setting. Kaplan-Meier methods were used to measure duration of response, progression-free survival (PFS), and overall survival (OS). RESULTS: The overall population (N = 160) included 74 patients (46.3%) with intrahepatic cholangiocarcinoma, 41 (25.6%) with extrahepatic cholangiocarcinoma, and 45 (28.1%) with gallbladder cancer. Thirty unique 2 L regimens were recorded for the study population, with folinic acid, fluorouracil and oxaliplatin (FOLFOX, 34.4%) and capecitabine monotherapy (20.0%) being the most common. ORR was 7.5% (95% CI, 3.9%-12.7%). From 2 L initiation, median PFS was 2.8 months (95% CI, 2.4-3.3 months), and median OS was 5.2 months (95% CI, 4.2-6.7 months). CONCLUSION: Results from this study provide real-world evidence that although patients treated in the community oncology setting receive a wide variety of 2 L treatments, the regimens are consistent with those recommended by guidelines. Although responses are observed with 2 L treatment, duration is brief and associated with poor OS in patients with advanced or metastatic disease.


Assuntos
Neoplasias dos Ductos Biliares , Neoplasias do Sistema Biliar , Colangiocarcinoma , Adulto , Humanos , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Neoplasias dos Ductos Biliares/patologia , Fluoruracila/uso terapêutico , Ductos Biliares Intra-Hepáticos/patologia , Neoplasias do Sistema Biliar/patologia
4.
Eur Radiol ; 31(3): 1578-1587, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32902745

RESUMO

OBJECTIVES: To compare liver stiffness measurement (LSM) provided by Canon 2D-shear wave elastography (2D-SWE) and transient elastography (TE), the latter being the reference method. METHODS: Prospective study conducted in four European centres from 2015 to 2016 including patients with various chronic liver diseases who had LSMs with both 2D-SWE and TE on the same day. Median of 10 valid measurements (in kPa) was used for comparison using paired t test, Pearson correlation, intraclass correlation coefficient (ICC) and Bland-Altman plot. The ability of 2D-SWE to stratify patient according to recognised LSM-TE thresholds was assessed by ROC curve analysis. RESULTS: Six hundred forty patients were scanned, where 593 (92.7%), 572 (89.4%) and 537 (83.9%) had reliable LSMs by TE, 2D-SWE and both combined, respectively. In the latter (n = 537, 310 [57.7%] male, mean 55.3 ± 14.8 years), median LSM-TE and LSM-2D-SWE had a mean of 10.1 ± 9.4 kPa (range 2.4-75) and 9.1 ± 6.1 kPa (range 3.6-55.7) (paired t test: p < 0.001), respectively. These were significantly correlated (Pearson r = 0.932, p < 0.001, ICC 0.850 (0.825-0.872), bias 0.99 ± 4.33 kPa [95% limits of agreement - 9.48 to + 7.49] with proportional error towards higher LSM values). LSM-2D-SWE values significantly increased with TE categories (ANOVA: p < 0.001). AUROCs ranged from 0.935 ± 0.010 (95% CI 0.910-0.954) to 0.973 ± 0.009 (95% CI 0.955-0.985), resulting in correct classification of 390/537 (73%) patients. Three 2D-SWE measurements were sufficient for reliable LSMs. CONCLUSION: LSM using 2D-SWE correlates well with TE. It tends to underestimate higher stages of liver fibrosis but correctly classifies the majority of patients. It may be used in TE-derived algorithms to manage patients. KEY POINTS: • Liver stiffness measurement (LSM) by 2D-shear wave elastography (2D-SWE) and transient elastography (TE) are strongly correlated. • 2D-SWE shows proportionately lower LSM values compared to TE, particularly with the higher LSM range. • Three individual measurements by 2D-SWE are sufficient to assess LSM reliably.


Assuntos
Técnicas de Imagem por Elasticidade , Humanos , Fígado/diagnóstico por imagem , Cirrose Hepática/diagnóstico por imagem , Masculino , Estudos Prospectivos , Reprodutibilidade dos Testes
6.
Future Oncol ; 16(16): 1069-1081, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32374623

RESUMO

Gemcitabine/cisplatin is standard of care for first-line treatment of patients with advanced biliary tract cancer (aBTC); new treatments are needed. NUC-1031 is designed to overcome key cancer resistance mechanisms associated with gemcitabine. The tolerability/efficacy signal of NUC-1031/cisplatin in the Phase Ib ABC-08 study suggested that this combination may represent a more efficacious therapy than gemcitabine/cisplatin for patients with aBTC, leading to initiation of the global NuTide:121 study which will include 828 patients ≥18 years with untreated histologically/cytologically-confirmed aBTC (including cholangiocarcinoma, gallbladder or ampullary cancer); randomized (1:1) to NUC-1031 (725 mg/m2)/cisplatin (25 mg/m2) or gemcitabine (1000 mg/m2)/cisplatin (25 mg/m2), on days 1/8, Q21-days. Primary objectives are overall survival and objective response rate. Secondary objectives: progression-free survival, safety, pharmacokinetics, patient-reported quality of life and correlative studies. (Investigational new drug (IND) number: 139058, European Clinical Trials database: EudraCT Number 2019-001025-28, ClinicalTrials.gov identifier: NCT04163900).


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Ductos Biliares Intra-Hepáticos/efeitos dos fármacos , Neoplasias do Sistema Biliar/tratamento farmacológico , Colangiocarcinoma/tratamento farmacológico , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Ductos Biliares Intra-Hepáticos/patologia , Neoplasias do Sistema Biliar/patologia , Colangiocarcinoma/patologia , Cisplatino/administração & dosagem , Monofosfato de Citidina/administração & dosagem , Monofosfato de Citidina/análogos & derivados , Desoxicitidina/administração & dosagem , Desoxicitidina/análogos & derivados , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Metástase Neoplásica , Estadiamento de Neoplasias , Taxa de Sobrevida , Resultado do Tratamento , Adulto Jovem , Gencitabina
7.
Chemistry ; 26(17): 3661-3687, 2020 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-31709642

RESUMO

The two enantiomers of a compound often have profoundly different biological properties and thus their liability to racemisation in aqueous solutions is an important piece of information. The authors reviewed the available data concerning the process of racemisation in vivo, in the presence of biological molecules (e.g., racemase enzymes, serum albumin, cofactors and derivatives) and under purely chemical but aqueous conditions (acid, base and other aqueous systems). Mechanistic studies are described critically in light of reported kinetic data. The types of experimental measurement that can be used to effectively determine rate constants of racemisation in various conditions are discussed and the data they provide is summarised. The proposed origins of enzymatic racemisation are presented and suggest ways to promote the process that are different from processes taking place in bulk water. Experimental and computational studies that provide understanding and quantitative predictions of racemisation risk are also presented.


Assuntos
Racemases e Epimerases/química , Albumina Sérica/química , Cinética , Estereoisomerismo
8.
Expert Opin Drug Discov ; 14(6): 527-539, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30882254

RESUMO

INTRODUCTION: Racemization has long been an ignored risk in drug development, probably because of a lack of convenient access to good tools for its detection and an absence of methods to predict racemization risk. As a result, the potential effects of racemization have been systematically underestimated. Areas covered: Herein, the potential effects of racemization are discussed through a review of drugs for which activity and side effects for both enantiomers are known. Subsequently, drugs known to racemize are discussed and the authors review methods to predict racemization risk. Application of a method quantitatively predicting racemization risk to databases of compounds from the medicinal chemistry literature shows that success in clinical trials is negatively correlated with racemization risk. Expert opinion: It is envisioned that a quantitative method of predicting racemization risk will remove a blind spot from the drug development pipeline. Removal of the blind spot will make drug development more efficient and result in less late-stage attrition of the drug pipeline.


Assuntos
Química Farmacêutica/métodos , Desenvolvimento de Medicamentos/métodos , Descoberta de Drogas/métodos , Desenho de Fármacos , Humanos , Preparações Farmacêuticas/química , Estereoisomerismo
9.
JMIR Res Protoc ; 8(1): e11545, 2019 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-30664496

RESUMO

BACKGROUND: Colorectal cancer is one of the most common cancers and causes of cancer-related death. Up to approximately 70% of patients with metastatic colorectal cancer (mCRC) have metastases to the liver at initial diagnosis. Second-line systemic treatment in mCRC can prolong survival after development of disease progression during or after first-line treatment and in those who are intolerant to first-line treatment. OBJECTIVE: The objective of this study is to evaluate the efficacy and safety of transarterial radioembolization (TARE) with TheraSphere yttrium-90 (90Y) glass microspheres combined with second-line therapy in patients with mCRC of the liver who had disease progression during or after first-line chemotherapy. METHODS: EPOCH is an open-label, prospective, multicenter, randomized, phase 3 trial being conducted at up to 100 sites in the United States, Canada, Europe, and Asia. Eligible patients have mCRC of the liver and disease progression after first-line chemotherapy with either an oxaliplatin-based or irinotecan-based regimen and are eligible for second-line chemotherapy with the alternate regimen. Patients were randomized 1:1 to the TARE group (chemotherapy with TARE in place of the second chemotherapy infusion and subsequent resumption of chemotherapy) or the control group (chemotherapy alone). The addition of targeted agents is permitted. The primary end points are progression-free survival and hepatic progression-free survival. The study objective will be considered achieved if at least one primary end point is statistically significant. Secondary end points are overall survival, time to symptomatic progression defined as Eastern Cooperative Oncology Group Performance Status score of 2 or higher, objective response rate, disease control rate, quality-of-life assessment by the Functional Assessment of Cancer Therapy-Colorectal Cancer questionnaire, and adverse events. The study is an adaptive trial, comprising a group sequential design with 2 interim analyses with a planned maximum of 420 patients. The study is designed to detect a 2.5-month increase in median progression-free survival, from 6 months in the control group to 8.5 months in the TARE group (hazard ratio [HR] 0.71), and a 3.5-month increase in median hepatic progression-free survival time, from 6.5 months in the control group to 10 months in the TARE group (HR 0.65). On the basis of simulations, the power to detect the target difference in either progression-free survival or hepatic progression-free survival is >90%, and the power to detect the target difference in each end point alone is >80%. RESULTS: Patient enrollment ended in October 2018. The first interim analysis in June 2018 resulted in continuation of the study without any changes. CONCLUSIONS: The EPOCH study may contribute toward the establishment of the role of combination therapy with TARE and oxaliplatin- or irinotecan-based chemotherapy in the second-line treatment of mCRC of the liver. TRIAL REGISTRATION: ClinicalTrials.gov NCT01483027; https://clinicaltrials.gov/ct2/show/NCT01483027 (Archived by WebCite at http://www.webcitation.org/734A6PAYW). INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR1-10.2196/11545.

10.
J Chem Inf Model ; 59(1): 98-116, 2019 01 28.
Artigo em Inglês | MEDLINE | ID: mdl-30462505

RESUMO

A framework is presented for the calculation of novel alignment-free descriptors of molecular shape. The methods are based on the technique of spectral geometry which has been developed in the field of computer vision where it has shown impressive performance for the comparison of deformable objects such as people and animals. Spectral geometry techniques encode shape by capturing the curvature of the surface of an object into a compact, information-rich representation that is alignment-free while also being invariant to isometric deformations, that is, changes that do not distort distances over the surface. Here, we adapt the technique to the new domain of molecular shape representation. We describe a series of parametrization steps aimed at optimizing the method for this new domain. Our focus here is on demonstrating that the basic approach is able to capture a molecular shape into a compact and information-rich descriptor. We demonstrate improved performance in virtual screening over a more established alignment-free method and impressive performance compared to a more accurate, but much more computationally demanding, alignment-based approach.


Assuntos
Processamento de Imagem Assistida por Computador , Estrutura Molecular , Algoritmos , Simulação por Computador , Bases de Dados de Compostos Químicos , Modelos Moleculares
11.
JMIR Res Protoc ; 7(8): e11234, 2018 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-30111528

RESUMO

BACKGROUND: Globally, hepatocellular carcinoma is the second most common cause of cancer deaths. It remains challenging to intensify cancer treatment without impairing liver function. OBJECTIVE: The objective of the TheraSphere in the Treatment of Patients with Unresectable Hepatocellular Carcinoma (STOP-HCC) study is to examine the hypothesis that transarterial radioembolization (TheraSphere yttrium-90 glass microspheres) combined with standard first-line treatment with sorafenib will improve outcomes over treatment with sorafenib alone in unresectable hepatocellular carcinoma. The STOP-HCC study is the largest international, multicenter, prospective study of intra-arterial treatment in combination with sorafenib in unresectable hepatocellular carcinoma. Here we report the study design. METHODS: STOP-HCC is a prospective, phase 3, open-label, randomized controlled study conducted across up to 105 sites in North America, Europe, and Asia. Eligible adults have unresectable hepatocellular carcinoma and a life expectancy of at least 12 weeks, 1 or more unidimensional measurable lesions, Child-Pugh score 7 points or less, and Eastern Cooperative Oncology Group Performance Status score 1 or lower, and are candidates for treatment with sorafenib. Presence of branch portal vein tumor thrombosis is permitted. Patients were randomly assigned in a 1:1 ratio to receive either sorafenib alone or transarterial radioembolization followed by sorafenib within 2 to 6 weeks. The primary outcome is overall survival. Secondary outcomes are time to progression, time to untreatable progression, time to symptomatic progression, tumor response, quality of life, and adverse event occurrence. The study is an adaptive trial, comprising a group-sequential design with 2 interim analyses with 520 patients, and an option to increase the sample size to 700 patients at the second interim analysis. The sample size of 520 patients allows for 417 deaths to give 80% power to detect an increase in median overall survival from 10.7 months for the sorafenib group (based on the Sorafenib Hepatocellular Carcinoma Assessment Randomized Protocol [SHARP] trial) to 14.2 months for the transarterial radioembolization+sorafenib group (hazard ratio 0.754) with 2-sided alpha of .05. The increased sample size of 700 patients allows for 564 deaths to give 80% power to detect a smaller difference in median overall survival from 10.7 months for the sorafenib group to 13.7 months for the transarterial radioembolization+sorafenib group (hazard ratio 0.781). RESULTS: Enrollment for the study completed in September 2017. Results of the first and second interim analyses were reviewed by the Independent Data Monitoring Committee. The recommendation of the committee, at both interim analyses, was to continue the study without any changes. CONCLUSIONS: The STOP-HCC study will contribute toward the establishment of the role of combination therapy with transarterial radioembolization and sorafenib in the treatment of unresectable hepatocellular carcinoma with and without branch portal vein tumor thrombosis. TRIAL REGISTRATION: ClinicalTrials.gov NCT01556490; https://clinicaltrials.gov/ct2/show/NCT01556490 (Archived by WebCite at http://www.webcitation.org/7188iygKs). REGISTERED REPORT IDENTIFIER: RR1-10.2196/11234.

14.
J Chem Inf Model ; 58(4): 747-760, 2018 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-29600850

RESUMO

We present an algorithm, ReFlex3D, for the refinement of flexible molecular alignments based on their three-dimensional shape and electrostatic properties. The algorithm is designed to be used with fast conformer generators to refine an initial overlay between two molecules and thus to obtain improved overlaps as judged by an increase in calculated similarity values. ReFlex3D is open-source and built as a python package working in combination with the OEChem Toolkit. As such it can readily be implemented in existing workflows ranging from the selection of compounds from a virtual screening campaign to the construction of similarity based prediction models to estimate binding affinities. We evaluate ReFlex3D against the AstraZeneca Validation Test Set and illustrate its potential within a predictive model compared to an established method (Posit).


Assuntos
Algoritmos , Modelos Moleculares , Eletricidade Estática , Cristalografia por Raios X , Conformação Molecular , Linguagens de Programação
15.
Ultrasound Int Open ; 4(1): E2-E15, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29423461

RESUMO

"How to perform contrast-enhanced ultrasound (CEUS)" provides general advice on the use of ultrasound contrast agents (UCAs) for clinical decision-making and reviews technical parameters for optimal CEUS performance. CEUS techniques vary between centers, therefore, experts from EFSUMB, WFUMB and from the CEUS LI-RADS working group created a discussion forum to standardize the CEUS examination technique according to published evidence and best personal experience. The goal is to standardise the use and administration of UCAs to facilitate correct diagnoses and ultimately to improve the management and outcomes of patients.

16.
ChemMedChem ; 13(6): 607-613, 2018 03 20.
Artigo em Inglês | MEDLINE | ID: mdl-29314719

RESUMO

Bioisosterism is an important concept in the lead optimisation phase of drug discovery where the aim is to make modifications to parts of a molecule in order to improve some properties while maintaining others. We present an analysis of bioisosteric fragments extracted from the ligands in an established data set consisting of 121 protein targets. A pairwise analysis is carried out of all ligands for a given target. The ligands are fragmented using the BRICS fragmentation scheme and a pair of fragments is deemed to be bioisosteric if they occupy a similar volume of the protein binding site. We consider two levels of generality, one which does not consider the number of attachment points in the fragments and a more restricted case in which both fragments are required to have the same number of attachments. We investigate the extent to which the bioisosteric pairs that are found are common across different target.


Assuntos
Algoritmos , Biologia Computacional , Bases de Dados de Proteínas , Proteínas/química , Descoberta de Drogas , Ligantes , Conformação Proteica
17.
Abdom Radiol (NY) ; 43(1): 127-142, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28819825

RESUMO

Contrast-enhanced ultrasound (CEUS) is a specialized form of ultrasound (US) performed with an intravenous injection of microbubble contrast agents. It has been successfully used for a variety of applications including characterization of liver tumors. In April 2014, the American College of Radiology (ACR) convened a working group of international experts to develop ACR CEUS Liver Imaging Reporting and Data System (CEUS LI-RADS). An initial version of CEUS LI-RADS was published in August 2016. Although the CEUS LI-RADS concept and principles for liver lesion characterization, using dynamic contrast enhancement features, are similar to those for CT or MRI, there are significant differences between CT/MRI and CEUS LI-RADS. Therefore, CEUS LI-RADS has different diagnostic features and a unique characterization algorithm. The size of a lesion, the type and degree of arterial phase enhancement, the presence of washout, and the timing and degree of washout are the major features used for categorization. This paper describes key differences between CT/MRI and CEUS, and provides a diagnostic algorithm of CEUS LI-RADS with detailed, step-by-step instructions and imaging examples of CEUS LI-RADS categories.


Assuntos
Algoritmos , Carcinoma Hepatocelular/diagnóstico por imagem , Meios de Contraste/administração & dosagem , Neoplasias Hepáticas/diagnóstico por imagem , Ultrassonografia/métodos , Carcinoma Hepatocelular/patologia , Diagnóstico Diferencial , Humanos , Neoplasias Hepáticas/patologia , Imageamento por Ressonância Magnética/métodos , Sensibilidade e Especificidade , Tomografia Computadorizada por Raios X/métodos
18.
Angew Chem Int Ed Engl ; 57(4): 982-985, 2018 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-29072355

RESUMO

Racemization has a large impact upon the biological properties of molecules but the chemical scope of compounds with known rate constants for racemization in aqueous conditions was hitherto limited. To address this remarkable blind spot, we have measured the kinetics for racemization of 28 compounds using circular dichroism and 1 H NMR spectroscopy. We show that rate constants for racemization (measured by ourselves and others) correlate well with deprotonation energies from quantum mechanical (QM) and group contribution calculations. Such calculations thus provide predictions of the second-order rate constants for general-base-catalyzed racemization that are usefully accurate. When applied to recent publications describing the stereoselective synthesis of compounds of purported biological value, the calculations reveal that racemization would be sufficiently fast to render these expensive syntheses pointless.

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