Effect of N -methyl deuteration on pharmacokinetics and pharmacodynamics of enzalutamide

Precision Deuteration in Search of Anticancer Agents: Approaches to Cancer Drug Discovery

Cancer chemotherapy has been shifted from conventional cytotoxic drug therapy to selective and target-specific therapy after the findings about DNA changes and proteins that are responsible for cancer. A large number of newer drugs were discovered as targeted therapy for particular types of neoplastic disease. The initial discovery includes the development of the first in the category, imatinib, a Bcr-Abl tyrosine kinase inhibitor (TKI) for the treatment of chronic myelocytic leukemia in 2001. But the joy did not last for long as the drug developed a point mutation within the ABL1 kinase domain of BCR-ABL1, which subsequently led to the discovery of many other TKIs. Resistance was observed for newer TKIs a few years after their launching, but the use of TKIs in life-threatening cancer therapy is considered as far better compared with the risks of disease because of its target specificity and hence less toxicity. In search of a better anticancer agent, the physiochemical properties of the lead molecule have been modified for its efficacy toward disease and delay in the development of resistance. Deuteration in the drug molecule is one of such modifications that alter the pharmacokinetic properties, generally its metabolism, as compared with its pharmacodynamic effects. Precision deuteration in many anticancer drugs has been carried out to search for better drugs for cancer. In this review, the majority of anticancer drugs and molecules for which deuteration was applied to get better anticancer molecules were discussed. This review will provide a complete guide about the benefits of deuteration in cancer chemotherapy.

Deuterium in drug discovery: progress, opportunities and challenges

Substitution of a hydrogen atom with its heavy isotope deuterium entails the addition of one neutron to a molecule. Despite being a subtle change, this structural modification, known as deuteration, may improve the pharmacokinetic and/or toxicity profile of drugs, potentially translating into improvements in efficacy and safety compared with the non-deuterated counterparts. Initially, efforts to exploit this potential primarily led to the development of deuterated analogues of marketed drugs through a 'deuterium switch' approach, such as deutetrabenazine, which became the first deuterated drug to receive FDA approval in 2017. In the past few years, the focus has shifted to applying deuteration in novel drug discovery, and the FDA approved the pioneering de novo deuterated drug deucravacitinib in 2022. In this Review, we highlight key milestones in the field of deuteration in drug discovery and development, emphasizing recent and instructive medicinal chemistry programmes and discussing the opportunities and hurdles for drug developers, as well as the questions that remain to be addressed.

Effect of position of deuterium atoms on gas chromatographic isotope effects

Deuterium substitution provides various benefits in drug molecules, including improvement in pharmacokinetic properties, reduction of toxicity, reduction of epimerization, etc. Also, it has been shown that the position of deuterium substitution affects the properties of drug molecules. Therefore, it is important to study low molecular weight deuterated isotopologues which constitute the deuterated pool and are building blocks of larger deuterated molecules. The effect of the position and number of deuterium atoms on the retention of 23 deuterated isotopologues on two gas chromatography stationary phases of different polarities was evaluated. It was observed that the ratio of calculated chromatographic isotope effects resulting from a deuterium atom connected to an sp² vs. an sp³ hybridized carbon was more on the polar IL-111i stationary phase compared to the nonpolar PDMS-5, for each group of isotopologues. Also, a compound with a deuterium atom connected to an sp² hybridized carbon always had greater retention than the analogous compound where deuterium was connected to an sp³ hybridized carbon. The van't Hoff plots for all analytes showed that the effect of entropy was almost negligible in the separation of deuterated vs. protiated isotopologues, thus these separations were mainly enthalpy driven.

Effect of deuteration on the single dose pharmacokinetic properties and postoperative analgesic activity of methadone

Although methadone is effective in the management of acute pain, the complexity of its absorption-distribution-metabolism-excretion profile limits its use as an opioid of choice for perioperative analgesia. Because deuteration is known to improve the pharmacokinetic, pharmacodynamic and toxicological properties of some drugs, here we characterized the single dose pharmacokinetic properties and post-operative analgesic efficacy of d9-methadone. The pharmacokinetic profiles of d9-methadone and methadone administered intravenously to CD-1 male mice revealed that deuteration leads to a 5.7- and 4.4-fold increase in the area under the time-concentration curve and maximum concentration in plasma, respectively, as well as reduction in clearance (0.9 ± 0.3 L/h/kg vs 4.7 ± 0.8 L/h/kg). The lower brain-to-plasma ratio of d9-methadone compared to that of methadone (0.35 ± 0.12 vs 2.05 ± 0.62) suggested that deuteration decreases the transfer of the drug across the blood-brain barrier. The estimated LD50 value for a single intravenous dose of d9-methadone was 2.1-fold higher than that for methadone. Moreover, d9-methadone outperformed methadone in the efficacy against postoperative pain by primarily activating peripheral opioid receptors. Collectively, these data suggest that the replacement of three hydrogen atoms in three methyl groups of methadone altered its pharmacokinetic properties, improved safety, and enhanced its analgesic efficacy.

Recent Updates on the Development of Deuterium-Containing Drugs for the Treatment of Cancer

Cancer is one of the deadliest diseases in the world. In 2020, 19.3 million cancer cases and 10 million deaths were reported in the world. It is supposed that the prevalence of cancer cases will rise to 28.4 million by 2040. Chemotherapy-based regimens have a narrow therapeutic index, severe adverse drug reactions, and lack metabolic stability. Besides, the metabolism of anticancer produces several non-active and toxic metabolites that reduce exposure of the target site to the parent drug. Therefore, developing better-tolerated and effective new anticancer drugs and modification of the existing anticancer drugs to minimize toxicity and increase efficacy has become a very urgent need. Deuterium incorporation reduces the metabolism of certain drugs that are breakdown by pathways involving hydrogen-carbon bond scission. For example, CYP450 mediated oxidative metabolism of drugs that involves the breakdown of a hydrogen-carbon bond affected by deuteration. Deuterium incorporation into the drug increases the half-life and reduces the dose, which provides better safety and efficacy. Deutetrabenazine is the first deuterated form of tetrabenazine approved to treat chorea associated with Huntington’s disease and tardive dyskinesia. The study revealed that Deutetrabenazine has fewer neuropsychiatric side effects with favorable safety than tetrabenazine. The current review highlights the deuterium kinetic isotope effect on drug metabolism, deuterated compound pharmacokinetic property, and safety profile. Besides, this review explains the deuterated anticancer drug development update status.

Rhodium-Catalyzed Deuterated Tsuji-Wilkinson Decarbonylation of Aldehydes with Deuterium Oxide

The recent surge in the applications of deuterated drug candidates has rendered an urgent need for diverse deuterium labeling techniques. Herein, an efficient Rh-catalyzed deuterated Tsuji-Wilkinson decarbonylation of naturally available aldehydes with D₂O is developed. In this reaction, D₂O not only acts as a deuterated reagent and solvent but also promotes Rh-catalyzed decarbonylation. In addition, decarbonylative strategies for the synthesis of terminal monodeuterated alkenes from α,β-unsaturated aldehydes are within reach.

Phase I clinical trial of HC-1119 soft capsule in Chinese healthy adult male subjects: Pharmacokinetics and safety of single-dose proportionality and effects of food

BACKGROUND

Preclinical studies showed that HC-1119, a deuterated version of enzalutamide, could competitively inhibit androgen binding to androgen receptor by blocking the transmission of androgen receptor signaling pathway as enzalutamide, inducing apoptosis of prostate cancer cells and reducing the proliferation of prostate cancer cells. Animal pharmacokinetic studies also show that deuterization of enzalutamide as HC-1119 could retain the basic properties of mother drug, increases the stability of compounds to metabolic enzymes and the drug exposure in vivo, prolong the half-life and reduce the production of metabolites, which may lead to a better efficacy and safety of HC-1119 compared with enzalutamide.

METHODS

To evaluate the pharmacokinetics and safety of HC-1119 and the effects of food on pharmacokinetics in healthy adult Chinese men after single-dose administration of HC-1119. A total of 47 Chinese healthy adult male subjects received HC-1119 soft capsule at a single oral dose of 40, 80, or 160 mg followed on fasting or 160 mg after high-fat meal respectively. HC-1119 prototype and its metabolites M1 and M2 in plasma were collected individually in a total 23 time points. Pharmacokinetics were determined by sensitive LC/MS/MS for dose-proportionality study.

RESULTS

In subjects taking HC-1119 soft capsules on fasting, C_max of HC-1119 prototype increased dose-dependently. Either C_max and AUC_0-∞ of M1 or C_max of M2 showed statistically significant difference. Dose-proportionality evaluation showed linear pharmacokinetic characteristics in C_max of HC-1119 prototype, C_max and AUC_0-∞ of M2 in dose range of 40-160 mg. C_max of HC-1119 was significantly different between the two groups as 160 mg HC-1119 on fasting or after a high-fat diet respectively, while the other parameter were not. HC-1119 and its metabolites M1 and M2 showed a linear dynamic trend.

CONCLUSIONS

HC-1119 is expected to have lower clinical dose than the similar drug enzalutamide. The absorption of HC-1119 and the main pharmacokinetic parameters of HC-1119 and its metabolites M1 and M2 were not affected by high-fat diet. The clinical application of HC-1119 soft capsule in the later stage can be recommended for both fasting and postprandial. The safety and tolerance were good in this population.

A Randomized Phase 1 Evaluation of Deupirfenidone, a Novel Deuterium-Containing Drug Candidate for Interstitial Lung Disease and Other Inflammatory and Fibrotic Diseases

LYT-100 (deupirfenidone) is a selectively deuterated form of pirfenidone under development for the treatment of inflammatory and fibrotic diseases, including interstitial lung disease. Adverse events associated with antifibrotics can be a barrier to adoption and persistence in patients with interstitial lung diseases, most of whom are not on standard-of-care therapy. LYT-100 is designed to have a differentiated pharmacokinetic (PK) profile from pirfenidone and could offer a differentiated safety profile compared to current standard-of-care drugs while retaining the biochemical potency and specificity of pirfenidone. We conducted a phase 1b study to ascertain the safety, tolerability, steady-state PK profile, and food effect of LYT-100. This was a 2-part study. Part 1 assessed multiple ascending doses of LYT-100 from 100, 250, 500, 750, and 1000 mg twice daily given over 5 days without titration. Part 2 assessed the effects of fed vs fasting conditions on the PK profile of a single 500-mg dose of LYT-100. All doses up to 1000 mg were well tolerated, with adverse events being mild and transient. Exposure was slightly lower in the fed condition. LYT-100 was well tolerated and has a dose-proportional PK profile. The ratio of parent to major metabolite concentration was higher than reported with pirfenidone, which is consistent with an effect of deuteration on metabolism. No maximum tolerated dose was identified up to 1000 mg twice-daily dosing. These results support further clinical development of LYT-100, particularly considering the adverse event profile of current standard-of-care drugs.

Phase I clinical trial of HC-1119: A deuterated form of enzalutamide

The purpose of our study was to investigate the safety, pharmacokinetics (PK), and initial antitumor efficacy of HC-1119 in patients with metastatic castration-resistant prostate cancer (mCRPC). Eligible mCRPC patients were included in our study (NCT03774056) with two parts. Part A was a dose escalation study in which patients received a dose escalation of HC-1119 (40, 80, 160 and 200 mg/day). Part B was a dose expansion study in which patients received HC-1119 at the dose of 80 and 160 mg. Safety assessment and pharmacokinetic samplings were performed for all patients at the given time points; preliminary tumor response was also assessed. Twenty-four patients were enrolled in part A and 19 patients in part B, respectively. HC-1119 was safe, well tolerated and no dose-limiting toxicity was observed. Fatigue was the most common treatment-related adverse event and no seizures were observed. At the dose levels of 40, 80 and 160 mg, the AUC and C_max of HC-1119 in plasma increased almost dose-proportionally at the steady state in mCRPC patients. Maximum prostate-specific antigen (PSA) response rates (≥50% reduction from the baseline) in dose escalation and dose expansion cohorts were 77% and 75%, respectively; the overall disease control rate (22 patients available for imaging analysis) was 72.7%, with PR in 4 patients, SD in 12 patients and PD in 6 patients; the 2-year overall survival rate in patients from Part B was 56.8%. HC-1119 was safe, well tolerated and efficacious and HC-1119 at 80 mg/day is recommended for further studies.

Discovery and biological evaluation of darolutamide derivatives as inhibitors and down-regulators of wild-type AR and the mutants

Androgen receptor (AR) has been a target of prostate cancer (PC) for nearly six decades. Recently, downregulating or degrading AR and the mutants especially the splice variant 7 (AR-V7) lacking ligand binding domain (LBD) emerged as an advantageous therapeutic approach to overcome drug resistance. Here, the structural modification of darolutamide resulted in the discovery of dual-action AR inhibitors and down-regulators. Unlike other traditional AR antagonists targeting the AR-LBD, compounds 4k and 4b not only inhibit the activities of wt-AR and AR-F876L mutant but also downregulate the protein expression of full-length (AR-full) and AR variant 7 (AR-V7) at mRNA level. In cell proliferation assays, compounds 4k and 4b exhibited better antiproliferative activities than darolutamide and enzalutamide against AR-V7-positive 22Rv1 cells and VCaP cells. In addition, 4k demonstrated better antitumor activity than clinically used enzalutamide in castration-resistant VCaP xenograft model. Collectively, combining the activities of AR inhibition and downregulation, compound 4k is proposed as an advantageous lead compound to disrupt AR signaling and overcome resistance.

A highly selective H/D exchange reaction of 1,4-dihydropyridines

Herein, we report a simple, economical, and effective acid-mediated method for the in situ deuteration of Hantzsch esters and their 4-substituted derivatives, including some drugs that constitute important calcium channel blockers which are effective for hypertension treatment. Hydrogen isotope exchange occurred selectively at α-alkyl C-H bonds in the 2,6-substituents.

Generation and use of tritiated borane in situ for formamide tritiation to an N-methyl-3 H group

The synthesis of [N-methyl-3 H](+/-)-mecamylamine is described as an example of a convenient and mild method to reduce formamide groups using tritiated borane generated in situ. The product was characterized by thin layer chromatography, high performance liquid chromatography, mass spectrometry, and tritium NMR.