Pharmacokinetic considerations for drugs that treat diarrhea-predominant irritable bowel syndrome: what's new?

INTRODUCTION: Irritable bowel syndrome (IBS), which presents a significant healthcare and socioeconomic burden, is one of the main issues in the field of therapy. Hence, it is imperative to tackle this matter by evaluating the safety and efficacy of the available treatments and determining the ideal approach for each patient. AREAS COVERED: We reviewed the pharmacokinetics and safety of pharmacologic interventions administered in diarrhea-predominant IBS (IBS-D) patients. PubMed, Google Scholar and the USFDA databases were searched up to November 2023 to include all updated information on eluxadoline, alosetron, and rifaximin. EXPERT OPINION: The most effective way to treat IBS-D is to focus on managing the most common symptoms. However, healthcare providers face a challenge when it comes to identifying the right treatment for each patient, and the root cause of this is the diversity of IBS-D population. Studies have shown that there are differences in how men and women metabolize drugs, which may lead to gender-specific adverse reactions. Women tend to have higher drug concentrations in their bloodstream and take longer to eliminate them. Therefore, healthcare providers may need to reduce the dosage for female patients. Integrating IBS care into sustainable development efforts can indirectly contribute to achieving SDGs and promote health and well-being for all.

PORT: A Randomized, Cross-Over, Phase 2 Study of Melflufen Peripheral Versus Central Intravenous Administration in Patients With Relapsed/Refractory Multiple Myeloma.

BACKGROUND: Melflufen, a first-in-class alkylating peptide-drug conjugate, rapidly enters tumor cells and metabolizes to melphalan. In previous studies, melflufen was administered via central venous catheter (CVC). However, administration by peripheral venous catheter (PVC) may be preferable. PATIENTS AND METHODS: PORT was a two-period, phase 2 crossover study of CVC versus PVC melflufen administration in patients with relapsed/refractory multiple myeloma. Adults with ≥ 2 prior therapies refractory to/intolerant of an immunomodulatory drug and a proteasome inhibitor were randomized 1:1 to weekly oral dexamethasone plus melflufen (40 mg) via CVC or PVC infusion on day 1 of 28-day cycle 1. In cycle 2, patients continued dexamethasone and crossed over to the other melflufen administration route. In cycle 3, all patients received melflufen until progression; PVC or CVC routes were allowed based upon investigator decision. Pharmacokinetic sampling was performed during and after melflufen infusion. Primary endpoints were melphalan pharmacokinetic parameters (Cmax, AUC(0-t), and AUC(0-∞)) and frequency and severity of PVC-related local reactions. RESULTS: The 90% CIs for adjusted geometric mean ratios for pharmacokinetic parameters following CVC versus PVC administration were within the 0.8-1.25 bioequivalence range (Cmax 0.946 [90% CI: 0.849, 1.053]; AUC(0-t) 0.952 [90% CI: 0.861, 1.053]; AUC(0-∞) 0.955 [90% CI: 0.863, 1.058]). In both arms, adverse events were primarily hematological and similar; no phlebitis or local infusion-related reactions occurred. CONCLUSION: Melflufen PVC and CVC administrations are bioequivalent based on melphalan pharmacokinetic parameters. Melflufen via PVC was well tolerated, with no infusion-related reactions or new safety signals and may represent an alternative route of administration.

A bis-boron boramino acid PET tracer for brain tumor diagnosis.

PURPOSE: Boramino acids are a class of amino acid biomimics that replace the carboxylate group with trifluoroborate and can achieve the 18F-labeled positron emission tomography (PET) and boron neutron capture therapy (BNCT) with identical chemical structure. METHODS: This study reports a trifluoroborate-derived boronophenylalanine (BBPA), a derived boronophenylalanine (BPA) for BNCT, as a promising PET tracer for tumor imaging. RESULTS: Competition inhibition assays in cancer cells suggested the cell accumulation of [18F]BBPA is through large neutral amino acid transporter type-1 (LAT-1). Of note, [18F]BBPA is a pan-cancer probe that shows notable tumor uptake in B16-F10 tumor-bearing mice. In the patients with gliomas and metastatic brain tumors, [18F]BBPA-PET shows good tumor uptake and notable tumor-to-normal brain ratio (T/N ratio, 18.7 ± 5.5, n = 11), higher than common amino acid PET tracers. The [18F]BBPA-PET quantitative parameters exhibited no difference in diverse contrast-enhanced status (P = 0.115-0.687) suggesting the [18F]BBPA uptake was independent from MRI contrast-enhancement. CONCLUSION: This study outlines a clinical trial with [18F]BBPA to achieve higher tumor-specific accumulation for PET, provides a potential technique for brain tumor diagnosis, and might facilitate the BNCT of brain tumors.

Fluorinated borono-phenylalanine for optimizing BNCT: Enhancing boron absorption against hydrogen scattering for thermal neutrons.

BACKGROUND: Boron-containing compounds, such as 4-borono-phenylalanine (BPA) are used as drugs for cancer treatment in the framework of Boron Neutron Capture Therapy (BNCT). Neutron irradiation of boron-rich compounds delivered to cancer cells triggers nuclear reactions that destroy cancer cells. PURPOSE: We provide a modeling of the thermal neutron cross section of BPA, a drug used in Boron Neutron Capture Therapy (BNCT), to quantify the competing contributions of boron absorption against hydrogen scattering, for optimizing BNCT by minimizing the latter. METHODS: We perform the experimental determination of the total neutron scattering cross section of BPA at thermal and epithermal neutron energies using neutron transmission measurements. We isolate the contribution related to the incoherent scattering by hydrogen atoms as a function of the neutron energy by means of the Average Functional Group Approximation, and we calculate the probability for a neutron of being absorbed as a function of the neutron energy both for BPA and for its variants where either one or all four aromatic hydrogen atoms are substituted by 19 F, and both for the samples with natural occurrence or enriched concentration of 10 B. RESULTS: While referring to the already available literature for in vivo use of fluorinated BPA, we show that fluorine-rich variants of BPA increase the probability of neutrons being captured by the molecule. As the higher absorption efficiency of fluorinated BPA does not depend on whether the molecule is used in vivo or not, our results are promising for the higher efficiency of the boron neutron capture treatment. CONCLUSIONS: Our results suggest a new advantage using fluorinated compounds for BNCT, in their optimized interaction with neutrons, in addition to their already known capability to be used for monitoring and pharmacokinetics studies using 19 F-Nuclear Magnetic Resonance or in 18 F-Positron Emission Tomography.

mPEG-b-P(Glu-co-Phe) nanoparticles increase gastric retention time and gastric ulcer treatment efficacy of 20(S)-ginsenoside Rg3.

BACKGROUND: Gastric ulcer (GU) belongs to gastric mucosal irritation and damage. 20(S)-ginsenoside Rg3 (Rg3) has shown anti-oxidant, antiinflammation, and tissue repair effects which are essential for GU treatment. However, the solubility of Rg3 is poor and low gastrointestinal absorption may limit its anti-ulcer effects. As a result, we aim to increase the gastric retention time and gastric absorption of Rg3 to achieve better GU treatment efficacy. METHODS: The mPEG-b-P(Glu-co-Phe) nanoparticles loaded with Rg3 (Rg3-NPs) were developed. The characteristics of Rg3-NPs, including the morphology, diameter, and stability were analyzed. The Rg3 release profiles, gastric retention of Rg3, in vitro cytotoxicity, and pharmacokinetics of Rg3 were assessed. An alcohol-induced rats GU model was performed, and the rats were randomly separated into five treatment groups. Biochemical analysis, gross evaluation, histopathology, and immunohistochemical analysis were applied to further analyze the anti-ulcer effects of Rg3-NPs. RESULTS: Rg3-NPs were successfully prepared and the Rg3 release was pH sensitive. The gastric retention time of Rg3 is longer in Rg3-NPs group than that in Rg3 group. By slightly increasing nitric oxide (NO), obviously increasing epidermal growth factor (EGF), EGF receptor (EGFR), and superoxide dismutase (SOD), and decreasing endothelin-1 (ET-1) and nitric oxide synthase (NOS2), Rg3-NPs possess better GU treatment efficacy than Rg3. CONCLUSIONS: Rg3-NPs can increase gastric retention time and gastric absorption of Rg3 and promote its GU treatment efficacy.

Comparison of Arterial-Venous Balance and Tracer Incorporation Methods for Measuring Muscle Fractional Synthesis and Fractional Breakdown Rates.

Loss of muscle mass in response to injury or immobilization impairs functional capacity and metabolic health, thus hindering rehabilitation. Stable isotope techniques are powerful in determining skeletal muscle protein fluxes. Traditional tracer incorporation methods to measure muscle protein synthesis and breakdown are cumbersome and invasive to perform in vulnerable populations such as children. To circumvent these issues, a two-bolus stable isotope amino acid method has been developed; although, measured rates of protein synthesis and breakdown have not been validated simultaneously against an accepted technique such as the arterial-venous balance method. The purpose of the current analysis was to provide preliminary data from the simultaneous determination of the arteriovenous balance and two-bolus tracer incorporation methods on muscle fractional synthesis and breakdown rates in children with burns. Five were administered a primed-constant infusion of L-[15N]Threonine for 180 minutes (Prime: 8 µmol/kg; constant: 0.1 µmol·kg-1·minute-1). At 120 and 150 minutes, bolus injections of L-[ring-13C6]Phenylalanine and L-[15N]Phenylalanine (50 µmol/kg each) were administered, respectively. Blood and muscle tissue samples were collected to assess mixed muscle protein synthesis and breakdown rates. The preliminary results from this study indicate that there is no difference in either fractional synthesis rate (mean ± SD; arteriovenous balance: 0.19 ± 0.17 %/h; tracer incorporation: 0.14 ± 0.08 %/h; P = .42) or fractional breakdown rate (arteriovenous balance: 0.29 ± 0.22 %/h; tracer incorporation: 0.23 ± 0.14 %/h; P = .84) between methods. These data support the validity of both methods in quantifying muscle amino acid kinetics; however, the results are limited and adequately powered research is still required.

Boron Neutron Capture Therapy (BNCT) for Cutaneous Malignant Melanoma Using 10B-p-Boronophenylalanine (BPA) with Special Reference to the Radiobiological Basis and Clinical Results.

BNCT is a radiotherapeutic method for cancer treatment that uses tumor-targeting 10B-compounds. BNCT for cutaneous melanoma using BPA, a phenylalanine derivative, was first initiated by Mishima et al. in 1987. This article reviews the radiobiological basis of melanoma control and damage to normal tissues as well as the results of clinical studies. Experimental studies showed that the compound biological effectiveness (CBE) values of the 10B (n, α)7Li reaction for melanoma control ranged from 2.5 to 3.3. The CBE values of the 10B (n, α)7Li reaction for skin damage ranged from 2.4 to 3.7 with moist desquamation as the endpoint. The required single radiation dose for controlling human melanoma was estimated to be 25 Gy-Eq or more by analyzing the 50% tumor control dose data of conventional fractionated radiotherapy. From the literature, the maximum permissible dose to human skin by single irradiation was estimated to be 18 Gy-Eq. With respect to the pharmacokinetics of BPA in patients with melanoma treated with 85-350 mg/kg BPA, the melanoma-to-blood ratio ranged from 2.1-3.8 and the skin-to-blood ratio was 1.31 ± 0.22. Good local tumor control and long-term survival of the patients were achieved in two clinical trials of BNCT conducted in Japan.

Application of a PBPK model to elucidate the changes of systemic and liver exposures for rosuvastatin, carotegrast, and bromfenac followed by OATP inhibition in monkeys.

The impact of organic anion-transporting polypeptide (OATP) inhibition on systemic and liver exposures of three OATP substrates was investigated in cynomolgus monkeys. A monkey physiologically-based pharmacokinetic (PBPK) model was constructed to describe the exposure changes followed by OATP functional attenuation. Rosuvastatin, bromfenac, and carotegrast were administered as a single intravenous cassette dose (0.5 mg/kg each) in monkeys with and without predosing with rifampin (RIF; 20 mg/kg) orally. The plasma exposure of rosuvastatin, bromfenac, carotegrast, and OATP biomarkers, coproporphyrin I (CP-I) and CP-III were increased 2.3, 2.1, 9.1, 5.4, and 8.8-fold, respectively, when compared to the vehicle group. The liver to plasma ratios of rosuvastatin and bromfenac were reduced but the liver concentration of the drugs remained unchanged by RIF treatment. The liver concentrations of carotegrast, CP-I, and CP-III were unchanged at 1 h but increased at 6 h in the RIF-treated group. The passive permeability, active uptake, and biliary excretion were characterized in suspended and sandwich-cultured monkey hepatocytes and then incorporated into the monkey PBPK model. As demonstrated by the PBPK model, the plasma exposure is increased through OATP inhibition while liver exposure is maintained by passive permeability driven from an elevated plasma level. Liver exposure is sensitive to the changes of metabolism and biliary clearances. The model further suggested the involvement of additional mechanisms for hepatic uptakes of rosuvastatin and bromfenac, and of the inhibition of biliary excretion for carotegrast, CP-I, and CP-III by RIF. Collectively, impaired OATP function would not reduce the liver exposure of its substrates in monkeys.

Biodistribution and radiation dosimetry of D-isomer of 4-borono-2-[18F]fluoro-phenylalanine: A comparative PET/CT study with L-isomer in healthy human volunteers.

INTRODUCTION: L-isomer of 4-borono-2-18F-fluoro-phenylalanine (L-[18F]FBPA) was generally applied in clinic for boron neutron capture therapy (BNCT). With radiotracer validation, D-isomer of [18F]FBPA (D-[18F]FBPA) was found a higher tumor to normal brain tissue ratio (TBR) than its L-isomer on positron emission tomography (PET) in rat brain glioma. The present study was conducted as a first-in-human study to explore the biodistribution and radiation dosimetry of D-[18F]FBPA in healthy human volunteers, compared with L-[18F]FBPA. METHODS: D-[18F]FBPA or L-[18F]FBPA was injected intravenously. Five whole-body PET scans were performed for each subject in the next 2 h. Organ time-activity curves were drawn by measuring SUVmean in volumes of interest. Absorbed dose coefficient of target organs and effective dose (ED) were estimated on OLINDA/EXM. RESULTS: Two healthy volunteers (both males) and three healthy volunteers (2 males, 1 female) were intravenously injected with D-[18F]FBPA (5.5-7.2 MBq/kg) and L-[18F]FBPA (3.9-6.8 MBq/kg) respectively. Only limited accumulation of D-[18F]FBPA was observed in healthy human brain, pancreas, liver, spleen and skeleton. The ED was calculated to be 0.026 mSv/MBq. Urinary bladder wall received the highest dose of 0.28 mGy/MBq, followed by kidneys (0.06 mGy/MBq), and all the other organs received less than 0.03 mGy/MBq. For L-[18F]FBPA, higher uptake in brain, pancreas, liver, spleen and skeleton could be visualized, compared with D-[18F]FBPA. The ED of L-[18F]FBPA was 0.020 ± 0.001 mSv/MBq. Urinary bladder wall and kidneys still received the highest dose among organs but with lower values than those of D-[18F]FBPA. CONCLUSIONS: D-[18F]FBPA had lower activity in normal brain, liver, spleen, pancreas and skeleton, compared with its L-isomer. D-[18F]FBPA is safe from a radiological standpoint. ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE: D-[18F]FBPA was safe from a radiological standpoint, and had lower activity in normal brain, liver, spleen, pancreas and skeleton than its L-isomer. This study ensures the safety and validity of D-[18F]FBPA for further clinical trials in patients with cancer.

A Randomized, Double-Blind, Placebo- and Positive-Controlled, 4-Period Crossover Study of the Effects of Solriamfetol on QTcF Intervals in Healthy Participants.

Solriamfetol, a dopamine and norepinephrine reuptake inhibitor, is approved (United States and European Union; Sunosi) to treat excessive daytime sleepiness associated with narcolepsy (75-150 mg/day) or obstructive sleep apnea (37.5-150 mg/day). A thorough QT/QTc study assessed solriamfetol effects on QT interval (Fridericia correction for heart rate; QTcF). This randomized, double-blind, placebo- and positive-controlled, 4-period crossover study compared single doses of 300 and 900 mg solriamfetol, 400 mg moxifloxacin, and placebo in healthy adults. Placebo- and predose-adjusted mean differences in QTcF (ddQTcF; primary end point) were analyzed, and solriamfetol pharmacokinetics were characterized. Fifty-five participants completed all periods. Upper bounds of 2-sided 90% confidence intervals (CIs) for ddQTcF for both solriamfetol doses were <10 milliseconds at all postdose time points. Assay sensitivity was demonstrated with moxifloxacin; lower bounds of 2-sided 90%CIs for ddQTcF > 5 milliseconds at 1, 2, and 3 hours postdose. There were no QTcF increases > 60 milliseconds or QTcF values > 480 milliseconds at either solriamfetol dose. Solriamfetol median tmax was 2-3 hours; exposure was dose-proportional. More participants experienced adverse events (AEs) after solriamfetol 900 versus 300 mg (70% vs 29%); none were serious (all mild/moderate), and there were no deaths. Common AEs were nausea, dizziness, and palpitations. Neither solriamfetol dose resulted in QTcF prolongation > 10 milliseconds.

Uptake of dietary amino acids into arterial blood during continuous enteral feeding in critically ill patients and healthy subjects.

BACKGROUND: Amino acid availability is a regulatory factor of protein anabolism and is partly dependent on enteral amino acid uptake. During continuous enteral feeding, enteral amino acid uptake may vary considerably, but this has not been documented systematically. METHODS: In this pragmatic study, we investigated patients in the intensive care unit (n = 10) and healthy adults (n = 10). The time course of essential amino acid concentrations in arterial plasma and the uptake of dietary phenylalanine were recorded during 12 hours of continuous enteral feeding, using a 13C-labeled phenylalanine tracer. RESULTS: Plasma essential amino acid concentrations and 13C-phenylalanine enrichment reached a tentative steady state after no more than 4.5 h from start of tracer infusion. There was a large intra- and inter-individual variability in both cohorts. No periodicity could be detected in the temporal variation. CONCLUSION: During continuous enteral feeding, uptake of amino acids shows large intra- and inter-individual variation. A tentative steady state of 13C-phenylalanine uptake is eventually reached. TRIAL REGISTRATION: Registered at Australian New Zealand Clinical Trials Registry, trial ID ACTRN12616000593437.

Preclinical evaluation of new α-radionuclide therapy targeting LAT1: 2-[211At]astato-α-methyl-L-phenylalanine in tumor-bearing model.

INTRODUCTION: Targeted α-radionuclide therapy has attracted attention as a promising therapy for refractory cancers. However, the application is limited to certain types of cancer. Since L-type amino acid transporter 1 (LAT1) is highly expressed in various human cancers, we prepared an LAT1-selective α-radionuclide-labeled amino acid analog, 2-[211At]astato-α-methyl-L-phenylalanine (2-[211At]AAMP), and evaluated its potential as a therapeutic agent. METHODS: 2-[211At]AAMP was prepared from the stannyl precursor. Stability of 2-[211At]AAMP was evaluated both in vitro and in vivo. In vitro studies using an LAT1-expressing human ovarian cancer cell line, SKOV3, were performed to evaluate cellular uptake and cytotoxicity of 2-[211At]AAMP. Biodistribution and therapeutic studies in SKOV3-bearing mice were performed after intravenous injection of 2-[211At]AAMP. RESULTS: 2-[211At]AAMP was stable in murine plasma in vitro and excreted intact into urine. Cellular uptake of 2-[211At]AAMP was inhibited by treatment with an LAT1-selective inhibitor. After 24 h incubation, 2-[211At]AAMP suppressed clonogenic growth at 10 kBq/ml, and induced cell death and DNA double-strand breaks at 25 kBq/ml. When injected into mice, 2-[211At]AAMP exhibited peak accumulation in the tumor at 30 min postinjection, and radioactivity levels in the tumor were retained up to 60 min. The majority of the radioactivity was rapidly eliminated from the body into urine in an intact form immediately after injection. 2-[211At]AAMP significantly improved the survival of mice (P < 0.05) without serious side effects. CONCLUSION: 2-[211At]AAMP showed α-radiation-dependent cellular growth inhibition after it was taken up via LAT1. In addition, 2-[211At]AAMP had a beneficial effect on survival in vivo. These findings suggest that 2-[211At]AAMP would be useful for the treatment of LAT1-positive cancer. ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE: This is the first report of an LAT1-targeting radiopharmaceutical for α-radionuclide therapy; this agent would be applicable for the treatment of various types of cancer.

Pharmacokinetics of 10B-p-boronophenylalanine (BPA) in the blood and tumors in human patients: A critical review with special reference to tumor-to-blood (T/B) ratios using resected tumor samples.

We reviewed 10B concentration kinetics in the blood and tumors in human patients administered with BPA. The 10B concentration in the blood peaked at the end of intravenous infusion of BPA, followed by a biphasic-decreasing curve with half-lives for the first and second components of the curve being 0.7-3.7 and 7.2-12.0 h, respectively. The mean tumor-to-blood (T/B) ratio obtained from resected tumor samples was 3.40 ± 0.83 for melanoma and the ratio ranged from 1.4 to 4.7 for glioblastoma.

Difference in BPA uptake between glioma stem-like cells and their cancerous cells.

Tumor sphere-forming (TS) glioma stem cells and cancerous TS cells were analyzed in vivo and in vitro. The boron concentration in murine TS tumors was higher than normal tissue. The boron concentration at 24 h was 0.80 ± 0.09 µg/107 in the TS cells, and 1.08 ± 0.08 µg/107 in the cancerous cells. The LAT-1 amino-acid transporter positive rate was 35.4% in the TS cells and 100% in the cancerous cells. These results suggested the relation between LAT-1 expression and boronophenylalanine concentration in vitro.

Phenylalanine stable isotope tracer labeling of cow milk and meat and human experimental applications to study dietary protein-derived amino acid availability.

BACKGROUND & AIMS: Availability of dietary protein-derived amino acids (AA) is an important determinant for their utilization in metabolism and for protein synthesis. Intrinsic labeling of protein is the only method to directly trace availability and utilization. The purpose of the present study was to produce labeled milk and meat proteins and investigate how dietary protein-derived AA availability is affected by the protein-meal matrix. METHODS: Four lactating cows were infused with L-[ring-d5]phenylalanine and one with L-[15N]phenylalanine for 72 h. Milk was collected, and three of the [d5]phenylalanine cows were subsequently slaughtered. Two human studies were performed to explore plasma AA availability properties utilizing the labeled proteins. One study compared the intake of whey protein either alone or together with carbohydrates-fat food-matrix. The other study compared the intake of meat hydrolysate with minced beef. Cow blood, milk, meat and human blood samples were collected and analyzed by mass spectrometry. RESULTS: Whey and caseinate acquired label to 15-20 mol percent excess (MPE), and the meat proteins reached 0.41-0.73 MPE. The [d5]phenylalanine appeared fast in plasma and peaked 30 min after whey protein alone and meat hydrolysate intake, whereas whey protein with a food-matrix and the meat minced beef postponed the [d5]phenylalanine peak until 2 and 1 h, respectively. CONCLUSIONS: Phenylalanine stable isotope-labeled milk and meat were produced and proved a valuable tool to investigate AA absorption characteristics. Dietary protein in food-matrices showed delayed postprandial plasma AA availability as compared to whey protein alone and meat hydrolysate.

Design, Synthesis, and Mechanism Study of Benzenesulfonamide-Containing Phenylalanine Derivatives as Novel HIV-1 Capsid Inhibitors with Improved Antiviral Activities.

The HIV-1 CA protein has gained remarkable attention as a promising therapeutic target for the development of new antivirals, due to its pivotal roles in HIV-1 replication (structural and regulatory). Herein, we report the design and synthesis of three series of benzenesulfonamide-containing phenylalanine derivatives obtained by further structural modifications of PF-74 to aid in the discovery of more potent and drug-like HIV-1 CA inhibitors. Structure-activity relationship studies of these compounds led to the identification of new phenylalanine derivatives with a piperazinone moiety, represented by compound 11l, which exhibited anti-HIV-1NL4-3 activity 5.78-fold better than PF-74. Interestingly, 11l also showed anti-HIV-2ROD activity (EC50 = 31 nM), with almost 120 times increased potency over PF-74. However, due to the higher significance of HIV-1 as compared to HIV-2 for the human population, this manuscript focuses on the mechanism of action of our compounds in the context of HIV-1. SPR studies on representative compounds confirmed CA as the binding target. The action stage determination assay demonstrated that these inhibitors exhibited antiviral activities with a dual-stage inhibition profile. The early-stage inhibitory activity of compound 11l was 6.25 times more potent as compared to PF-74 but appeared to work via the accelerating capsid core assembly rather than stabilization. However, the mechanism by which they exert their antiviral activity in the late stage appears to be the same as PF-74 with less infectious HIV-1 virions produced in their presence, as judged p24 content studies. MD simulations provided the key rationale for the promising antiviral potency of 11l. Additionally, 11l exhibited a modest increase in HLM and human plasma metabolic stabilities as compared to PF-74, as well as a moderately improved pharmacokinetic profile, favorable oral bioavailability, and no acute toxicity. These studies provide insights and serve as a starting point for subsequent medicinal chemistry efforts in optimizing these promising HIV inhibitors.

Solriamfetol for Excessive Sleepiness in Narcolepsy and Obstructive Sleep Apnea.

OBJECTIVE: The purpose of this article is to review the available clinical trial data that led to the Food and Drug Administration (FDA) approval of solriamfetol as well as its role in clinical practice. DATA SOURCES: A MEDLINE/PubMed search was conducted (January 2000 to February 2020) using the keyword solriamfetol to discover appropriate clinical trials. STUDY SELECTION AND DATA EXTRACTION: Articles were included that were published in the English language and related to the FDA approval of solriamfetol or provided novel information regarding this drug entity. DATA SYNTHESIS: The findings of the review show that solriamfetol may be a safe and effective option for the treatment of excessive sleepiness (ES) related to narcolepsy and obstructive sleep apnea (OSA). RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE: Solriamfetol is distinguished from other stimulants in that it has lower binding affinity to dopamine and norepinephrine transporters and does not have the monoamine-releasing effects of amphetamines at usual therapeutic doses. Because of solriamfetol's unique mechanism of action, there may be a reduction in abuse potential compared with the other currently FDA-approved options. CONCLUSIONS: In clinical trials, solriamfetol has shown dose-dependent improvement in wakefulness over placebo and adds another option for clinicians when treating ES in narcolepsy and OSA.

Diagnosis of bladder cancer using 18F-labeled α-methyl-phenylalanine tracers in a mouse model.

OBJECTIVE: Although 2-18F-fluoro-2-deoxy-glucose (18F-FDG) has established roles in the diagnosis of a variety of cancers, it has limited value in the detection of primary/recurrent lesions in the bladder, mainly because of interference by the pooled radioactivity in the urine. Our previous study revealed promising properties of L- and D-2-18F-α-methyl-phenylalanine (2-18F-FAMP) as radiotracers; i.e., their rapid blood clearance and low renal accumulation. In the present study we evaluated the utility of L- and D-2-18F-FAMP for imaging bladder cancer in a mouse model. METHODS: We used the human bladder cancer cell line HT1376 to prepare a bladder cancer xenograft model in mice bearing both orthotopic and subcutaneous tumors. Biodistribution and PET imaging studies were performed at 1 and 3 h after injection of L-2-18F-FAMP or D-2-18F-FAMP. 18F-FDG was used as a control. RESULTS: At 1 h after injection, greater accumulations of both L-2-18F-FAMP and D-2-18F-FAMP were observed in the orthotopic tumors compared to 18F-FDG. The orthotopic tumor-to-muscle ratio of D-2-18F-FAMP was significantly higher than that of 18F-FDG (p < 0.01), because of the rapid blood clearance of D-2-18F-FAMP. L-2-18F-FAMP showed the highest subcutaneous tumor-to-muscle ratio (p < 0.01) due to its high subcutaneous tumor uptake. Compared to L-2-18F-FAMP, D-2-18F-FAMP exhibited faster clearance and lower kidney accumulation. In the PET imaging studies, L- and D-2-18F-FAMP both clearly visualized the orthotopic bladder tumors at 1 h after injection. CONCLUSION: Our study showed that L-2-18F-FAMP and D-2-18F-FAMP have the potential to detect bladder cancer.

Protein Type, Protein Dose, and Age Modulate Dietary Protein Digestion and Phenylalanine Absorption Kinetics and Plasma Phenylalanine Availability in Humans.

BACKGROUND: Dietary protein ingestion stimulates muscle protein synthesis by providing amino acids to the muscle. The magnitude and duration of the postprandial increase in muscle protein synthesis rates are largely determined by dietary protein digestion and amino acid absorption kinetics. OBJECTIVE: We assessed the impact of protein type, protein dose, and age on dietary protein digestion and amino acid absorption kinetics in vivo in humans. METHODS: We included data from 18 randomized controlled trials with a total of 602 participants [age: 53 ± 23 y; BMI (kg/m2): 24.8 ± 3.3] who consumed various quantities of intrinsically l-[1-13C]-phenylalanine-labeled whey (n = 137), casein (n = 393), or milk (n = 72) protein and received intravenous infusions of l-[ring-2H5]-phenylalanine, which allowed us to assess protein digestion and phenylalanine absorption kinetics and the postprandial release of dietary protein-derived phenylalanine into the circulation. The effect of aging on these processes was assessed in a subset of 82 young (aged 22 ± 3 y) and 83 older (aged 71 ± 5 y) individuals. RESULTS: A total of 50% ± 14% of dietary protein-derived phenylalanine appeared in the circulation over a 5-h postprandial period. Casein ingestion resulted in a smaller (45% ± 11%), whey protein ingestion in an intermediate (57% ± 10%), and milk protein ingestion in a greater (65% ± 13%) fraction of dietary protein-derived phenylalanine appearing in the circulation (P < 0.001). The postprandial availability of dietary protein-derived phenylalanine in the circulation increased with the ingestion of greater protein doses (P < 0.05). Protein digestion and phenylalanine absorption kinetics were attenuated in older when compared with young individuals, with 45% ± 10% vs. 51% ± 14% of dietary protein-derived phenylalanine appearing in the circulation, respectively (P = 0.001). CONCLUSIONS: Protein type, protein dose, and age modulate dietary protein digestion and amino acid absorption kinetics and subsequent postprandial plasma amino acid availability in vivo in humans. These trials were registered at clinicaltrials.gov as NCT00557388, NCT00936039, NCT00991523, NCT01317511, NCT01473576, NCT01576848, NCT01578590, NCT01615276, NCT01680146, NCT01820975, NCT01986842, and NCT02596542, and at http://www.trialregister.nl as NTR3638, NTR3885, NTR4060, NTR4429, and NTR4492.

Poly(vinyl alcohol) boosting therapeutic potential of p-boronophenylalanine in neutron capture therapy by modulating metabolism.

In the current clinical boron neutron capture therapy (BNCT), p-boronophenylalanine (BPA) has been the most powerful drug owing to its ability to accumulate selectively within cancers through cancer-related amino acid transporters including LAT1. However, the therapeutic success of BPA has been sometimes compromised by its unfavorable efflux from cytosol due to their antiport mechanism. Here, we report that poly(vinyl alcohol) (PVA) can form complexes with BPA through reversible boronate esters in aqueous solution, and the complex termed PVA-BPA can be internalized into cancer cells through LAT1-mediated endocytosis, thereby enhancing cellular uptake and slowing the untoward efflux. In in vivo study, compared with clinically used fructose-BPA complexes, PVA-BPA exhibited efficient tumor accumulation and prolonged tumor retention with quick clearance from bloodstream and normal organs. Ultimately, PVA-BPA showed critically enhanced antitumor activity in BNCT. The facile technique proposed in this study offers an approach for drug delivery focusing on drug metabolism.