A Pilot Study of Dynamic 18F-DCFPyL PET/CT Imaging of Prostate Adenocarcinoma in High-Risk Primary Prostate Cancer Patients.

PURPOSE: The primary aim of this study was to investigate the pharmacokinetics of 18F-DCFPyL, an 18F-labeled PSMA-based ligand, and to explore the utility of early time point positron emission tomography (PET) imaging extracted from PET data to distinguish malignant primary prostate from benign prostate tissue. PROCEDURES: Ten consecutive patients with biopsy-proven high-risk prostate cancer underwent a dynamic 18F-DCFPyL PET/CT scan of the pelvis for the first 45 min post-injection (p.i.) followed by a static PET/CT at 2 h p.i. 18F-DCFPyL uptake values and kinetics were compared between benign prostate tissue and prostate cancer, including quantitative pharmacokinetic PET parameters extracted from 18F-DCFPyL time activity curves generated from dynamic data using a two-tissue compartment model and Patlak plots. RESULTS: 18F-DCFPyL uptake values were significantly higher in primary prostate tumors than those in benign prostatic hyperplasia (BPH) and normal prostate tissue at 5 min, 30 min, and 120 min p.i. (P = 0.0002), when examining both SUVmax and SUVmean values. The two-tissue compartment model found an overall influx value (Ki) of 0.063 in primary prostate cancer, demonstrating a Ki over 15-fold higher in malignant prostate tissue compared with BPH (Ki = 0.004) and normal prostate tissue (Ki = 0.005) (P = 0.0001). CONCLUSION: High-risk primary prostate cancer is readily identified on dynamic and static, delayed, 18F-DCFPyL PET images. The tumor-to-background ratio increases over time, with optimal 18F-DCFPyL PET/CT imaging at 120 min p.i. for evaluation of prostate cancer, but not necessarily ideal for clinical application. Primary prostate cancer demonstrates different uptake kinetics in comparison to BPH and normal prostate tissue. The 15-fold difference in Ki between prostate cancer and non-cancer (BPH and normal) tissues translates to an ability to distinguish prostate cancer from normal tissue at time points as early as 5 to 10 min p.i.

Development of a guar gum film with lysine clonixinate for periodontal treatments.

Periodontal pain is a public health problem derived from different conditions, including periodontal diseases, prosthetic complications, and even extractions performed by dentist. There are various treatments to control acute dental pain, being the administration of analgesics, such as Lysine Clonixinate (LC), a common practice. Unfortunately, higher and repeated dosages are usually required. The purpose of this work was to develop a prolonged release pharmaceutical form as an alternative treatment for dental pain. Hence, we conceived a film based on guar gum and loaded different concentrations of LC. We evaluated the film's appearance, brittleness, strength, and flexibility, and then chose one formulation for adequate characteristics. Subsequently, we assessed the morphology, thermal behavior, and swelling properties of the films (LC-free and -loaded). Finally, we performed the release studies of LC from the films in vitro using a simulated saliva medium and employed several mathematical models to evaluate the release kinetics. Guar gum is a natural polymer obtained from the endosperm of Cyamopsis tetragonolobus that presents properties such as biosafety, biocompatibility, and biodegradability. Thus, it represents a potential excipient for use in pharmaceutical formulations. Moreover, our results revealed that the LC-loaded film presented a high adherence, suitable swelling behavior, high LC content, and a prolonged drug release. Therefore, the LC-loaded film may be considered a potential option to be applied as an alternative to treat dental pain.

Oral aspirin or low dose of intravenous lysine acetylsalicylate in ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention.

AIM: To compare the pharmacodynamic effect of an oral loading dose of 'noncoated' ASA 300 mg vs. an intravenous bolus injection of lysine acetylsalicylate 150 mg in patients with STEMI undergoing pPCI. METHODS: This was a prospective single-center, open label, pharmacodynamic study, including nonconsecutive patients presenting at our catheterization laboratory with STEMI undergoing pPCI and not receiving ASA within the previous 7 days. Pharmacodynamic analyses were performed at five time points: baseline, and 1, 2, 4 and 12 h after the loading dose, and measured as ASA reaction units (ARU) by the Verify Now System. An ARU more than 550 was considered as nonresponsiveness to study drugs. The primary end point was the different rate of patients with ARU more than 550 at 2 h after the loading dose of oral vs. intravenous ASA. Secondary end points included the comparison of ARU more than 550 at the other time points and the comparison of continuous ARU at each time point. RESULTS: The study was planned with a sample size of 68 patients, but it was prematurely stopped due to slow enrollment after the inclusion of 23 patients, 12 randomized to oral ASA and 11 to intravenous lysine acetylsalicylate. At 2 h the rate of patients with ARU more than 550 was numerically but not significantly higher in patients receiving oral ASA as compared with intravenous lysine acetylsalicylate (33 vs. 14.2%; Δ -0.19, 95% confidence interval -0.59-0.21, P = 0.58). The difference over time was NS (P = 0.98), though the prevalence of ARU more than 550 was higher at the other time points. Both routes of administration reduced ARU values over time, though with no overall significant difference between profiles (P overall = 0.48). CONCLUSION: In patients with STEMI undergoing pPCI the rate of nonresponsiveness to ASA was not different comparing an oral 'noncoated' loading dose of ASA with an intravenous bolus injection of lysine acetylsalicylate. However, as patient enrollment was prematurely terminated, this study is underpowered to draw a definite conclusion.

Pharmacological Advantage of SIRT2-Selective versus pan-SIRT1-3 Inhibitors.

Because of their involvement in various biological pathways, the sirtuin enzyme family members SIRT1, SIRT2, and SIRT3 play both tumor-promoting and tumor-suppressing roles, based on the context and experimental conditions. Thus, an interesting question is whether inhibiting one of them or inhibiting all of them would be better for treating cancers. Pharmacologically, this is difficult to address, due in part to potential off-target effects of different compounds. Compounds with almost identical properties but differing in SIRT1-3 selectivity will be useful for addressing this question. Here, we have developed a pan SIRT1-3 inhibitor (NH4-6) and a SIRT2-selective inhibitor (NH4-13) with very similar chemical structures, with the only difference being the substitution of an ester bond to an amide bond. Such a minimal difference allows us to accurately compare the anticancer effect of pan SIRT1-3 inhibition and SIRT2-selective inhibition in cellular and mouse models. NH4-6 showed stronger cytotoxicity than NH4-13 in cancer cell lines. In mice, both inhibitors showed similar anticancer efficacy. However, NH4-6 is toxic to mice, which hinders the use of higher dosages. These results highlight the advantage of SIRT2-selective inhibitors as potential anticancer therapeutics.

Monitoring PSMA Responses to ADT in Prostate Cancer Patient-Derived Xenograft Mouse Models Using [18F]DCFPyL PET Imaging.

PURPOSE: PSMA overexpression has been associated with aggressive prostate cancer (PCa). However, PSMA PET imaging has revealed highly variable changes in PSMA expression in response to ADT treatment ranging from increases to moderate decreases. To better understand these PSMA responses and potential relationship to progressive PCa, the PET imaging agent, [18F]DCFPyL, was used to assess changes in PSMA expression in response to ADT using genomically characterized LuCaP patient-derived xenograft mouse models (LuCaP-PDXs) which were found to be sensitive to ADT (LuCaP73 and LuCaP136;CS) or resistant (LuCaP167;CR). METHODS: [18F]DCFPyL (2-(3-{1-carboxy-5-[(6-[18F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid) was used to assess PSMA in vitro (saturation assays) in LuCaP tumor membrane homogenates and in vivo (imaging/biodistribution) in LuCaP-PDXs. Control and ADT-treated LuCaPs were imaged before ADT (0 days) and 2-, 7-, 14-, and 21-days post-ADT from which tumor:muscle ratios (T:Ms) were determined and concurrently tumor volumes were measured (caliper). After the 21-day imaging, biodistributions and histologic/genomic (PSMA, AR) analysis were done. RESULTS: [18F]DCFPyL exhibited high affinity for PSMA and distinguished different levels of PSMA in LuCaP tumors. Post-ADT CS LuCaP73 and LuCaP136 tumor volumes significantly decreased at day 7 or 14 respectively vs controls, whereas the CR LuCaP167 tumor volumes were minimally changed. [18F]DCFPyL imaging T:Ms were increased 3-5-fold in treated LuCaP73 tumors vs controls, while treated LuCaP136 T:Ms remained unchanged which was confirmed by day 21 biodistribution results. For treated LuCaP167, T:Ms were decreased (~ 45 %) vs controls but due to low T:M values (<2) may not be indicative of PSMA level changes. LuCaP73 tumor PSMA histologic/genomic results were comparable to imaging/biodistribution results, whereas the results for other tumor types varied. CONCLUSION: Tumor responses to ADT varied from sensitive to resistant among these LuCaP PDXs, while only the high PSMA expressing LuCaP model exhibited an increase in PSMA levels in response to ADT. These models may be useful in understanding the clinical relevance of PSMA PET responses to ADT and potentially the relationship to disease progression as it may relate to the genomic signature.

In vitro dissolution behaviour and absorption in humans of a novel mixed l-lysine salt formulation of EPA and DHA.

INTRODUCTION: Supplements with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are generally oil-based formulations containing their triacylglycerols, phospholipids or ethyl-esters (EE). Recently, a l-lysine salt of carboxylic EPA and DHA became available (Lys-FFA), which necessitated to study its oral absorption and plasma kinetics in humans. OBJECTIVES: The in vitro dissolution characteristics, oral bioavailability and 48 h plasma profiles of EPA and DHA (as triacylglycerides) of Lys-FFA, relative to a commercially available oil-based EE supplement. METHODS: Dissociation of the lysine from the FFAs was studied in vitro applying simulated gastric (12 h) and intestinal (3 h) conditions. In an open label, randomized, two-way cross-over design, oral administration of Lys-FFA (500 mg EPA plus 302 mg DHA) versus EE (504 mg EPA plus 378 mg DHA) was studied over 48 h, in eight female volunteers. Plasma profiles of EPA and DHA were described by Area Under the Curve (AUC; 0-12 h), Cmax and Tmax. RESULTS: Dissolution studies with Lys-FFA showed complete dissociation under both conditions. In volunteers Lys-FFA showed rapid absorption and high bioavailability indicated by significant differences in both the AUC0-12hr and Cmax when compared to the EE comparator (p<0.001), with AUC0-12hr which was for EPA 5 times higher with Lys-FFA than with the EE formulation. CONCLUSION: This first-in-man study of Lys-FFA demonstrated rapid absorption of EPA and DHA and a considerably higher bioavailability compared to an EE supplement under fasting conditions. The release and absorption characteristics from this solid form offer several new options in terms of formulation technology and dosing.

Pharmacodynamics and pharmacokinetics of a new type of recombinant insulin Lisargine injection.

BACKGROUND: Recombinant insulin Lisargine is a new type of insulin. In this study, we aimed to compare its pharmacodynamic (PD) and pharmacokinetic (PK) with Lantus. METHODS: The PD test was performed by exploring the effect of single administration on blood glucose of normal rats and STZ-induced diabetic rats, and the effect of multiple administrations on blood glucose of STZ-induced diabetic rats. Further PD tests include receptor affinity test, receptor autophosphorylation test and adipocyte glucose uptake test. Four IU and 8 IU per dog Lisargine was used for PK test, insulin was measured and area under curve (AUC) was calculated. RESULTS: With single injection, Lisargine 1.5 IU/kg had significant hypoglycemic effects at 1 and 2 h, similar to that of Lantus. Lisargine 5 IU/kg and 10 IU/kg lowered the blood glucose of STZ-induced diabetic rats at 1, 2, 4 & 6 h significantly. With multiple injections, Lantus lowered blood glucose at 2, 4 & 6 h, Lisargine 2.5 IU/kg, 5 IU/kg, and 10 IU/kg lowered blood glucose at 2 & 4 h significantly, compared with vehicle. There was no difference for receptor affinity test, receptor autophosphorylation test and adipocyte glucose uptake test between Lisargine and Lantus. The PK of Lisargine and Lantus of healthy Beagle dogs was very similar. CONCLUSIONS: This animal study demonstrated that PK and PD of Lisargine and Lantus were similar, suggesting the bioequivalence of these products.

Lysine Bioavailability in School-Age Children Consuming Rice Is Reduced by Starch Retrogradation.

BACKGROUND: Rice is one of the most commonly consumed cereal grains and is part of staple diets in the majority of the world. However, it is regarded as an incomplete protein, with lysine being a limiting amino acid. OBJECTIVES: Our objectives were to determine the bioavailability of lysine in school-age children consuming cooked white rice and to assess the effect of rice starch retrogradation. METHODS: Bioavailability or metabolic availability (MA) of lysine was determined using the indicator amino acid oxidation (IAAO) method in a repeated-measures design. Six healthy school-age children (3 boys, 3 girls) with a mean ± SD age of 6.8 ± 0.98 y randomly received 4 crystalline l-lysine intakes (2, 6, 10, 14 mg · kg-1 · d-1), and 5 rice intakes to provide lysine at 8, 11, or 14 mg · kg-1 · d-1. The 14 mg · kg-1 · d-1 intakes were measured twice as warm rice and once as cold rice (to assess the impact of starch retrogradation on MA). Diets provided protein at 1.5 g · kg-1 · d-1 and calories at 1.7 times the participant's measured resting energy requirement, and were isonitrogenous. Breath samples were collected at baseline and during an isotopic steady state for 13C enrichment measurement. The MA of lysine from rice was determined by comparing the IAAO response of rice with l-lysine using the slope-ratio and single intake methods. Starch retrogradation was characterized using differential scanning calorimetry. RESULTS: MA of lysine in warm rice measured in school-age children was 97.5% and was similar to a repeated rice study (97.1%) within the same study population. MA of lysine was reduced significantly (P < 0.05) to 86.1% when the cooked rice was consumed cold, which corresponded to detectable starch retrogradation. CONCLUSIONS: To our knowledge, this is the first study to measure the MA of lysine from rice in school-age children. Although the bioavailability of lysine from rice is high, it can be reduced by retrogradation of its starch component.This trial was registered at clinicaltrials.gov as NCT04135040.

Metabolic Availability of Lysine in Milk and a Vegetarian Cereal-Legume Meal Determined by the Indicator Amino Acid Oxidation Method in Indian Men.

BACKGROUND: Lysine rich foods such as milk and legumes serve as important food additions to the lysine deficient cereal-based diets of vegetarian populations in low- and middle-income countries (LMICs) to alleviate the risk of quality corrected dietary protein inadequacy. Dietary protein quality can be determined by estimating the metabolic availability (MA) of lysine. OBJECTIVES: The study aimed to estimate the MA of lysine in spray-dried cow milk powder (SMP), heat-treated spray-dried cow milk powder (HSMP), and a habitually consumed cereal-legume based vegetarian meal (VM), using the indicator amino acid oxidation (IAAO) slope-ratio method. METHODS: The MA of lysine in SMP, HSMP, and VM was estimated in 7 healthy young men aged 19-24 y with BMI of 21.5 ± 0.5 kg/m2 in a repeated measures design. The IAAO response slopes with 2 graded lysine intakes (10.5 and 15.0 mg·kg-1·d-1) from the SMP and VM were compared with the response slope generated with 3 graded crystalline lysine intakes (6.0, 10.5, and 15.0 mg·kg-1·d-1) at the subrequirement level. To produce HSMP, pasteurized cow milk was heat treated and spray dried. The MA of lysine in HSMP was tested at a single level of lysine intake (15 mg·kg-1·d-1). A total of 8 IAAO experiments were conducted on each participant in randomized order. The IAAO slopes were estimated using a linear mixed-effect regression model. RESULTS: The MA of lysine in SMP, HSMP, and VM was 91.9%, 69.9%, and 86.6% respectively. CONCLUSIONS: Heat treatment reduced the MA of lysine by 22% in HSMP compared with SMP in healthy Indian adults. The lysine MA estimates can be used to optimize lysine limited cereal-based diets, with the addition of appropriately processed legumes and milk powder, to meet the protein requirement. This trial was registered at Clinical Trials Registry of India (http://ctri.nic.in) as CTRI/2019/08/020568.

Bioavailable Lysine, Assessed in Healthy Young Men Using Indicator Amino Acid Oxidation, is Greater when Cooked Millet and Stewed Canadian Lentils are Combined.

BACKGROUND: Pearl millet is the chief source of energy in the diet in some developing regions, but has a limited amount of indispensable amino acid lysine. Complementation with pulses like lentils can improve the protein quality of millet diets, but the knowledge of lysine bioavailability (BA) in millet and lentils is lacking. OBJECTIVES: The study objectives were to determine the BA of lysine in millet and lentils separately and to assess the effect of complementation of millet and lentils in a mixed meal format. METHODS: We studied 9 healthy young men (≤30 y; BMI <25) in a repeated-measure design using the indicator amino acid oxidation (IAAO) method, with L-[1-13C] phenylalanine as the indicator. Each subject completed 7 or 8 experiments in random order. On the reference diet, subjects received 4 graded levels of L-lysine (5, 8, 12, and 15 mg·kg-1.d-1) from a crystalline amino acid mixture patterned after egg protein; on the test diets, they received 3 levels of lysine (10, 12, and 15 mg·kg-1.d-1) from either steamed millet or stewed lentils; and on the complementation diet, they received 1 level of lysine from a mixed meal of steamed millet and stewed lentils. The BA of lysine and the effect of complementation were assessed by comparing the IAAO responses to the test diets and the complementation diet with the IAAO response to L-lysine intakes in the reference protein, using the slope ratio method. RESULTS: The BA of lysine was 97% from millet and 80% from lentils. Complementation of steamed millet with stewed lentils decreased the oxidation of L-[1-13C] phenylalanine by 27% (P < 0.05), signifying improved quality of the combined millet and lentil protein. CONCLUSIONS: Lysine has high BA but is still limiting in steamed pearl millet. Complementation with lentils in a 2:1 ratio is recommended to meet the lysine and protein requirements for adult men consuming a millet-based diet. This trial was registered at clinicaltrials.gov as NCT03674736 and NCT03339167.

l-Arginine/l-lysine functionalized chitosan-casein core-shell and pH-responsive nanoparticles: fabrication, characterization and bioavailability enhancement of hydrophobic and hydrophilic bioactive compounds.

This study aimed at developing novel oral self-assembled delivery systems for the encapsulation, protection, and controlled release of hydrophobic and hydrophilic bioactive compounds based on l-arginine (Arg)- or l-lysine (Lys)-functionalized chitosan-casein nanoparticles (NPs). The assembled casein (CA) was modified by NaOH and used as a template core for affinity binding with hydrophobic curcumin and hydrophilic egg white-derived peptides (EWDP) and then coated with Arg- or Lys-functionalized chitosan (CS) to stabilize the systems via electrostatic interaction. Dynamic light scattering and transmission electron microscopy examination revealed Arg/Lys-CS-CA NPs with the smallest particle size of 110/82 nm, pH-responsive properties, excellent storage stability until 28 days, and spherical shape. The encapsulation efficiency of curcumin and EWDP in the NPs ranged from 81-91%, 35-74% in Arg-CS-CA NPs, and 76-87%, 48-87% in Lys-CS-CA NPs varying with different pH values. Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry analysis were conducted to fully characterize the interaction mechanism of Arg/Lys-CS with CA, as well as the NP incorporation with curcumin and EWDP. The in vitro controlled release profile of the core-shell NPs was obtained up to 24 and 48 h for curcumin and EWDP, respectively. The simulated gastrointestinal digestion experiments confirmed that curcumin and EWDP had higher bioaccessibility in Arg/Lys-CS-CA NPs. This work offers a novel approach for producing core-shell and pH-responsive nanocarriers for oral delivery and bioavailability enhancement of both hydrophobic and hydrophilic bioactive compounds.

Active targeted ligand-aza-BODIPY conjugate for near-infrared photodynamic therapy in melanoma.

Active targeting compound, a non-iodinated derivative of IK-IK-I2-azaBODIPY (1a) was previously reported to preferentially bind melanoma over healthy cells. In this study, we evaluate the photodynamic therapy (PDT) efficiency on melanoma cells of 1a, together with its reversed sequence compound KI-KI-I2-azaBODIPY (1b) and a non-targeted control I2-azaBODIPY-NH2 (2). All three test compounds possess absorption wavelengths in the near-infrared (NIR) region (λmax between 678 and 687 nm) which alleviate melanin interference and allow deeper tissue penetration. In vitro studies revealed 1a and 1b are promising photosensitizers with enhanced singlet oxygen generation, have increased uptake by B16-F10 melanoma cells via clathrin-mediated endocytosis and good photocytotoxic efficacies. Ex vivo biodistribution assays showed both 1a and 1b accumulated in the tumour. In B16-F10 tumour bearing-C57BL/6 mice, 10 mg/kg of 1b and light irradiation was found to reduce tumour volume by up to 23% at day-3. Doubling the dosage of 1b (20 mg/kg) enhanced the antitumour effect, showing 96% maximum tumour volume reduction at day-7 and tumour growth suppression for up to 12 days.

The glycation level of milk protein strongly modulates post-prandial lysine availability in humans.

Industrial heat treatment of milk results in protein glycation. A high protein glycation level has been suggested to compromise the post-prandial rise in plasma amino acid availability following protein ingestion. In the present study, we assessed the impact of glycation level of milk protein on post-prandial plasma amino acid responses in humans. Fifteen healthy, young men (age 26 (SEM 1) years, BMI 24 (SEM 1) kg/m2) participated in this randomised cross-over study and ingested milk protein powder with protein glycation levels of 3, 20 and 50 % blocked lysine. On each trial day, arterialised blood samples were collected at regular intervals during a 6-h post-prandial period to assess plasma amino acid concentrations using ultra-performance liquid chromatography. Plasma essential amino acid (EAA) concentrations increased following milk protein ingestion, with the 20 and 50 % glycated milk proteins showing lower overall EAA responses compared with the 3 % glycated milk protein (161 (SEM 7) and 142 (SEM 7) v. 178 (SEM 9) mmol/l × 6 h, respectively; P ≤ 0·011). The lower post-prandial plasma amino acid responses were fully attributed to an attenuated post-prandial rise in circulating plasma lysine concentrations. Plasma lysine responses (incremental AUC) following ingestion of the 20 and 50 % glycated milk proteins were 35 (SEM 4) and 92 (SEM 2) % lower compared with the 3 % glycated milk protein (21·3 (SEM 1·4) and 2·8 (SEM 0·7) v. 33·3 (SEM 1·7) mmol/l × 6 h, respectively; P < 0·001). Milk protein glycation lowers post-prandial plasma lysine availability in humans. The lower post-prandial availability of lysine following ingestion of proteins with a high glycation level may compromise the anabolic properties of a protein source.

Semiquantitative Parameters in PSMA-Targeted PET Imaging with [18F]DCFPyL: Impact of Tumor Burden on Normal Organ Uptake.

PURPOSE: In this study, we aimed to quantitatively investigate the biodistribution of [18F]DCFPyL in patients with prostate cancer (PCa) and to determine whether uptake in normal organs correlates with an increase in tumor burden. PROCEDURES: Fifty patients who had been imaged with [18F]DCFPyL positron emission tomography/computed tomography (PET/CT) were retrospectively included in this study. Forty of 50 (80 %) demonstrated radiotracer uptake on [18F]DCFPyL PET/CT compatible with sites of PCa. Volumes of interests (VOIs) were set on normal organs (lacrimal glands, parotid glands, submandibular glands, liver, spleen, and kidneys) and on tumor lesions. Mean standardized uptake values corrected to lean body mass (SULmean) and mean standardized uptake values corrected to body weight (SUVmean) for normal organs were assessed. For the entire tumor burden, SULmean/max, SUVmean, tumor volume (TV), and the total activity in the VOI were obtained using tumor segmentation. A Spearman's rank correlation coefficient was used to investigate correlations between normal organ uptake and tumor burden. RESULTS: There was no significant correlation between TV with the vast majority of the investigated organs (lacrimal glands, parotid glands, submandibular glands, spleen, and liver). Only the kidney showed significant correlation: With an isocontour threshold at 50 %, left kidney uptake parameters correlated significantly with TV (SUVmean, ρ = - 0.214 and SULmean, ρ = - 0.176, p < 0.05, respectively). CONCLUSIONS: Only a minimal sink effect with high tumor burden in patients imaged with [18F]DCFPyL was observed. Other factors, such as a high intra-patient variability of normal organ uptake, may be a much more important consideration for personalized dosimetry with PSMA-targeted therapeutic agents structurally related to [18F]DCFPyL than the tumor burden.

Semiquantitative Parameters in PSMA-Targeted PET Imaging with [18F]DCFPyL: Intrapatient and Interpatient Variability of Normal Organ Uptake.

PURPOSE: Prostate-specific membrane antigen (PSMA)-targeted positron emission tomography (PET) imaging has impacted the management of patients with prostate cancer (PCa) in many parts of the world. PSMA-targeted endoradiotherapies are also being increasingly utilized and for these applications, the radiopharmaceutical distribution in normal organs is particularly important because it may limit the dose that can be delivered to tumors. In this study, we measured both interpatient and intrapatient variability of [18F]DCFPyL uptake in the most relevant normal organs. PROCEDURES: Baseline and 6-month follow-up PSMA-targeted [18F]DCFPyL PET/computed tomography (CT) scans from 39 patients with PCa were reviewed. Volumes of interest were manually drawn using the best visual approximation of the organ edge for both lacrimal glands, all four major salivary glands, the liver, the spleen, and both kidneys for all patients. The average SUVmean, the COVs, and intraclass correlation coefficients (ICCs) across scans were calculated. Bland-Altman analyses were performed for all organs to derive repeatability coefficients (RCs). RESULTS: The liver demonstrated the lowest interpatient variability (13.0 and 16.6 % at baseline and follow-up, respectively), while the spleen demonstrated the largest interpatient variability (44.6 and 51.0 % at baseline and follow-up, respectively). The lowest intrapatient variability was found in the spleen (ICC 0.86) while the highest intrapatient variability was in the kidneys (ICCs 0.40-0.50). Bland-Altman analyses showed 95 % repeatability coefficients for mean uptake > 40 % for multiple organs and were highest for the lacrimal glands, kidneys, and spleen. CONCLUSIONS: Normal organs demonstrate significant variability in uptake of the PSMA-targeted radiotracer [18F]DCFPyL. Depending on the organ, different contributions of interpatient and intrapatient factors affect the intrinsic variability. The RCs also vary significantly among the different organs were highest for the lacrimal glands, kidneys, and spleen. These findings may have important implications for the design of clinical protocols and personalized dosimetry for PSMA-targeted endoradiotherapies.

Site-Specific Conjugation of the Indolinobenzodiazepine DGN549 to Antibodies Affords Antibody-Drug Conjugates with an Improved Therapeutic Index as Compared with Lysine Conjugation.

Antibody-drug conjugates have elicited great interest recently as targeted chemotherapies for cancer. Recent preclinical and clinical data have continued to raise questions about optimizing the design of these complex therapeutics. Biochemical methods for site-specific antibody conjugation have been a design feature of recent clinical ADCs, and preclinical reports suggest that site-specifically conjugated ADCs generically offer improved therapeutic indices (i.e., the fold difference between efficacious and maximum tolerated doses). Here we present the results of a systematic preclinical comparison of ADCs embodying the DNA-alkylating linker-payload DGN549 generated with both heterogeneous lysine-directed and site-specific cysteine-directed conjugation chemistries. Importantly, the catabolites generated by each ADC are the same regardless of the conjugation format. In two different model systems evaluated, the site-specific ADC showed a therapeutic index benefit. However, the therapeutic index benefit is different in each case: both show evidence of improved tolerability, though with different magnitudes, and in one case significant efficacy improvement is also observed. These results support our contention that conjugation chemistry of ADCs is best evaluated in the context of a particular antibody, target, and linker-payload, and ideally across multiple disease models.

Evaluating liver uptake and distribution of different poly(2-methyl-2-oxazoline) modified lysine dendrimers following intravenous administration.

We report on the synthesis of four poly(2-methyl-2-oxazoline) modified lysine dendrimers with different residual groups or modifications on the dendrimer core, including: amino groups (positive charge), carboxyl groups (negative charge), and two drug molecules, one of which has a high log P. We looked at the in vivo distribution amongst three main liver cell types: hepatocytes, liver sinusoidal endothelial cells (LSECs) and Kupffer cells (KCs) and found differences in cell distribution and uptake concentrations dependent on these residual groups. In particular, the amino-functional polymer showed greater uptake by the hepatocytes whilst the carboxyl-functionalised polymer exhibited greater uptake by KCs and LSECs. These findings provide insight into which professional scavenger cells of the liver remove these types of nanoparticles from the bloodstream and we describe some of the design criteria to consider when creating novel drug delivery systems.

Intra-individual comparison of 68Ga-PSMA-11 and 18F-DCFPyL normal-organ biodistribution.

PURPOSE: Detailed data comparing the biodistribution of PSMA radioligands is still scarce, raising concerns regarding the comparability of different compounds. We investigated differences in normal-organ biodistribution and uptake variability between the two most commonly PSMA tracers in clinical use, 68Ga-PSMA-11 and 18F-DCFPyL. METHODS: This retrospective analysis included 34 patients with low tumor burden referred for PET/CT imaging with 68Ga-PSMA-11 and subsequently 18F-DCFPyL. Images were acquired with 4 cross-calibrated PET/CT systems. Volumes of interest were placed on major salivary and lacrimal glands, liver, spleen, duodenum, kidneys, bladder, blood-pool and muscle. Normal-organ biodistribution of both tracers was then quantified as SUVpeak and compared using paired tests, linear regression and Bland-Altman analysis. Between-patient variability was also assessed. Clinical and protocol variables were investigated for possible interference. RESULTS: For both tracers the highest uptake was found in the kidneys and bladder and low background activity was noted across all scans. In the quantitative analysis there was significantly higher uptake of 68Ga-PSMA-11 in the kidneys, spleen and major salivary glands (p <  0.001), while the liver exhibited slightly higher 18F-DCFPyL uptake (p = 0.001, mean bias 0.79 ± 1.30). The lowest solid-organ uptake variability was found in the liver (COV 21.9% for 68Ga-PSMA-11, 22.5% for 18F-DCFPyL). There was a weak correlation between 18F-DCFPyL uptake time and liver SUVpeak (r = 0.488, p = 0.003) and, accordingly, patients scanned at later time-points had a larger mean bias between the two tracers' liver uptake values (0.05 vs 1.46, p = 0.001). CONCLUSION: Normal tissue biodistribution patterns of 68Ga-PSMA-11 and 18F-DCFPyL were similar, despite subtle differences in quantitative values. Liver uptake showed an acceptable intra-patient agreement and low inter-patient variability between the two tracers, allowing its use as a reference organ for thresholding scans in the qualitative comparison of PSMA expression using these different tracers.

Simplified Methods for Quantification of 18F-DCFPyL Uptake in Patients with Prostate Cancer.

Radiolabeled prostate-specific membrane antigen (PSMA) PET has demonstrated promising results for prostate cancer (PCa) imaging. Quantification of PSMA radiotracer uptake is desired as it enables reliable interpretation of PET images, use of PSMA uptake as an imaging biomarker for tumor characterization, and evaluation of treatment effects. The aim of this study was to perform a full pharmacokinetic analysis of 2-(3-(1-carboxy-5-[(6-18F-fluoro-pyridine-3-carbonyl)-amino]-pentyl)-ureido)-pentanedioic acid (18F-DCFPyL), a second-generation 18F-labeled PSMA ligand. On the basis of the pharmacokinetic analysis (reference method), simplified methods for quantification of 18F-DCFPyL uptake were validated. Methods: Eight patients with metastasized PCa were included. Dynamic PET acquisitions were performed at 0-60 and 90-120 min after injection of a median dose of 313 MBq of 18F-DCFPyL (range, 292-314 MBq). Continuous and manual arterial blood sampling provided calibrated plasma tracer input functions. Time-activity curves were derived for each PCa metastasis, and 18F-DCFPyL kinetics were described using standard plasma input tissue-compartment models. Simplified methods for quantification of 18F-DCFPyL uptake (SUVs; tumor-to-blood ratios [TBRs]) were correlated with kinetic parameter estimates obtained from full pharmacokinetic analysis. Results: In total, 46 metastases were evaluated. A reversible 2-tissue-compartment model was preferred for 18F-DCFPyL kinetics in 59% of the metastases. The observed k4 was small, however, resulting in nearly irreversible kinetics during the course of the PET study. Hence, k4 was fixated (0.015) and net influx rate, Ki, was preferred as the reference kinetic parameter. Whole-blood TBR provided an excellent correlation with Ki from full kinetic analysis (R2 = 0.97). This TBR could be simplified further by replacing the blood samples with an image-based, single measurement of blood activity in the ascending aorta (image-based TBR, R2 = 0.96). SUV correlated poorly with Ki (R2 = 0.47 and R2 = 0.60 for SUV normalized to body weight and lean body mass, respectively), most likely because of deviant blood activity concentrations (i.e., tumor tracer input) in patients with higher tumor volumes. Conclusion:18F-DCFPyL kinetics in PCa metastases are best described by a reversible 2-tissue-compartment model. Image-based TBRs were validated as a simplified method to quantify 18F-DCFPyL uptake and might be applied to clinical, whole-body PET scans. SUV does not provide reliable quantification of 18F-DCFPyL uptake.

Pharmacokinetic Properties of Ibuprofen (IBU) From the Fixed-Dose Combination IBU/Caffeine (400/100 mg; FDC) in Comparison With 400 mg IBU as Acid or Lysinate Under Fasted and Fed Conditions-Data From 2 Single-Center, Single-Dose, Randomized Crossover Studies in Healthy Volunteers.

Rapid onset of analgesic action is linked with rapid absorption of analgesics (high maximum concentration [Cmax ] and short time to maximum concentration [tmax ]). After overnight fasting, ibuprofen lysinate reaches higher peak plasma levels (Cmax ) earlier than ibuprofen acid (tmax ) with comparable exposure (area under the plasma concentration-time curve [AUC]); however, subjects usually take ibuprofen with or within a short time of a meal. Therefore, pharmacokinetic (PK) studies under fed conditions may better characterize properties under real-life conditions. We investigated a new fixed-dose combination (FDC) of ibuprofen acid 400 mg and caffeine 100 mg in 2 single-dose, randomized, crossover PK studies in healthy subjects (both N = 36). The FDC was compared with ibuprofen 400 mg as acid and as lysinate after an overnight fast in Study 1, and with ibuprofen lysinate after a meal in Study 2. After fasting, results for ibuprofen in the FDC were comparable with those from ibuprofen acid alone. Caffeine did not affect the Cmax , tmax , and AUC. As expected, a higher Cmax and shorter tmax were observed with ibuprofen lysinates vs the FDC. Compared with administration after fasting, Cmax and tmax for ibuprofen lysinate administered postprandially were markedly different, while with FDC, these parameters were less sensitive to food intake. Taken after a meal, ibuprofen in the FDC reached tmax earlier than ibuprofen lysinate (median 1.25 vs 1.63 hours), and Cmax was approximately 13% higher, with comparable AUC, suggesting that the profile of ibuprofen was in favor of the FDC compared with ibuprofen lysinate. Thus, under real-life conditions, ibuprofen lysinate had no PK advantage over the FDC. All preparations were well tolerated.