(99m)Tc-labeled porphyrin-lipid nanovesicles.

Porphyrin-lipid nanovesicles (PLN) have been developed with intrinsic capabilities as activatable multimodal photonic contrast agents. Radiolabeling of PLN encapsulating drugs could eventually be able to provide quantitative in vivo information for diagnosing and treating diseases. In this study, we developed (99m)Tc-labeled porphyrin-lipid nanovesicles ((99m)Tc-PLN) as a cargo-encapsulated formulation without significant impact on liposome integrity and encapsulation stability. 50 mM calcein was encapsulated into PLN by probe sonication. The size of the PLN was about 150 nm. The PLN were then reacted with (99m)Tc using SnCl2 dissolved in 1 mM HCl as a reducing agent and incubated for 10 min at 22 °C. The radiolabeling efficiency and stability of (99m)Tc-PLN were evaluated by instant thin-layer chromatography and low-pressure liquid chromatography (LPLC). (99m)Tc labeling was successful with a >92% labeling efficiency. LPLC showed that the liposomal elution peaks of the porphyrin-lipid and the calcein overlapped with the radioactivity elution peak of (99m)Tc-labeled PLN. The (99m)Tc-labeling procedure did not change the size of PLN. Encapsulated calcein remained inert inside PLN. Thus, this work lays out a simple and effective radiolabeling method using SnCl2 in HCl in the preparation of (99m)Tc-PLN.

(99m)Tc-labeled therapeutic inhaled amikacin loaded liposomes.

The radiolabeling of the liposome surface can be a useful tool for in vivo tracking of therapeutic drug loaded liposomes. We investigated radiolabeling therapeutic drug (i.e. an antibiotic, amikacin) loaded liposomes with (99m)Tc, nebulization properties of (99m)Tc-labeled liposomal amikacin for inhalation ((99m)Tc-LAI), and its stability by size exclusion low-pressure liquid chromatography (LPLC). LAI was reacted with (99m)Tc using SnCl2 dissolved in ascorbic acid as a reducing agent for 10 min at room temperature. The labeled products were then purified by anion exchange resin. The purified (99m)Tc-LAI in 1.5% NaCl solution was incubated at 4 °C to assess its stability by LPLC. The purified (99m)Tc-LAI was subjected to studies with a clinically used nebulizer (PARI eFlow®) and the Anderson Cascade Impactor (ACI). The use of ascorbic acid at 0.91 mM resulted in a quantitative labeling efficiency. The LPLC profile showed that the liposomal peak of LAI detected by a UV monitor at both 200 nm and 254 nm overlapped with the radioactivity peak of (99m)Tc-LAI, indicating that (99m)Tc-LAI is suitable for tracing LAI. The ACI study demonstrated that the aerosol droplet size distribution determined gravimetrically was similar to that determined by radioactivity. The liposome surface labeling method using SnCl2 in 0.91 mM ascorbic acid produced (99m)Tc-LAI with a high labeling efficiency and stability that are adequate to evaluate the deposition and clearance of inhaled LAI in the lung by gamma scintigraphy.

Effect of chelator conjugation level and injection dose on tumor and organ uptake of 111In-labeled MORAb-009, an anti-mesothelin antibody.

INTRODUCTION: Radiolabeling of a monoclonal antibody (mAb) with a metallic radionuclide requires the conjugation of a bifunctional chelator to the mAb. The conjugation, however, can alter the physical and immunological properties of the mAb, consequently affecting its tumor-targeting pharmacokinetics. In this study, we investigated the effect of the amount of 2-(p-isothiocyanatobenzyl)-cyclohexyl-diethylenetriamine-pentaacetic acid (CHX-A″) conjugated to MORAb-009, a mAb directed against mesothelin, and the effect of MORAb dose on the biodistribution of (111)In-labeled MORAb-009. METHODS: We used nude mice bearing the A431/K5 tumor as a mesothelin-positive tumor model and the A431 tumor as a mesothelin-negative control. To find the optimal level of CHX-A″ conjugation, CHX-A″-MORAb-009 conjugates with 2.4, 3.5 and 5.5 CHX-A″ molecules were investigated. To investigate the effect of injected MORAb-009 dose on neutralizing the shed mesothelin in the circulation, biodistribution studies were performed after the intravenous co-injection of (111)In-labeled MORAb-009 (2.4 CHX-A″/MORAb-009) with three different doses: 0.2, 2 and 30 µg of MORAb-009. RESULTS: The tumor uptake in A431/K5 tumor was four times higher than that in A431 tumor, indicating that the tumor uptake in A431/K5 was mesothelin mediated. The conjugate with 5.5 CHX-A″ showed a lower isoelectric point (pI) and lower immunoreactivity (IR) than the 2.4 CHX-A″ conjugate. These differences were reflected in the biodistribution of the (111)In label. The (111)In-labeled MORAb-009 conjugated with 2.4 CHX-A″ produced higher tumor uptake and lower liver and spleen uptakes than the 5.5 CHX-A″ conjugate. The biodistribution studies also revealed that the tumor uptake was significantly affected by the injected MORAb-009 dose and tumor size. The 30-µg dose produced higher tumor uptake than the 0.2- and 2-µg doses, whereas the 30-µg dose produced lower liver and spleen uptakes than the 0.2-µg dose. CONCLUSION: This study demonstrates that the number of chelate conjugation and the injected dose are two important parameters to achieve high tumor and low non-target organ uptake of (111)In-labeled MORAb-009. This study also suggests that the injected dose of mAb could be individualized based on the tumor size or the blood level of shed antigen in a patient to achieve the ideal tumor-to-organ radioactivity ratios.

Comparative CYP3A4 inhibitory effects of venlafaxine, fluoxetine, sertraline, and nefazodone in healthy volunteers.

An antidepressant for use in the patient receiving concomitant drug treatment, over-the-counter medications, or herbal products should lack cytochrome P-450 (CYP) 3A4 inductive or inhibitory activity to provide the least likelihood of a drug-drug interaction. This study addresses the potential of 4 diverse antidepressants (venlafaxine, nefazodone, sertraline, and fluoxetine) to inhibit or induce CYP3A4. In a 4-way crossover design, 16 subjects received clinically relevant doses of venlafaxine, nefazodone, or sertraline for 8 days or fluoxetine for 11 days. Treatments were separated by a 7- to 14-day washout period and fluoxetine was always the last antidepressant taken. CYP3A4 activity was evaluated for each subject at baseline and following each antidepressant using the erythromycin breath test (EBT) and by the pharmacokinetics of alprazolam (ALPZ) after 2-mg dose of oral ALPZ. Compared to baseline, venlafaxine, sertraline, and fluoxetine caused no apparent inhibition or induction of erythromycin metabolism (P > 0.05). For nefazodone, a statistically significant inhibition was observed (P < 0.0005). Nefazodone was also the only antidepressant that caused a significant change in ALPZ disposition, decreasing its area under the concentration-versus-time curve (AUC; P < 0.01), and increasing its elimination half-life (16.4 vs. 12.3 hours; P < 0.05) compared with values at baseline. No significant differences were found in the pharmacokinetics of ALPZ with any of the other antidepressants tested. These results demonstrate in vivo that, unlike nefazodone, venlafaxine, sertraline, and fluoxetine do not possess significant metabolic inductive or inhibitory effects on CYP3A4.

Explanations and unresolved issues pertaining to the development of the Nuclear Pharmacy Compounding Guidelines.

OBJECTIVES: To provide background information related to the development of the Nuclear Pharmacy Compounding Guidelines, to discuss regulatory complexities related to radiopharmaceutical compounding practice, and to summarize the gaps in the current compounding regulations for radiopharmaceuticals. DATA SOURCES: The Guidelines closely follow the provisions of section 503A of the Federal Food, Drug, and Cosmetic Act (FD&C Act), the monographs and chapters related to pharmacy compounding in the United States Pharmacopeia (USP), and the recommended guidelines published by the American Society of Health-System Pharmacists. SUMMARY: The Food and Drug Administration Modernization Act (FDAMA) of 1997 established parameters under which the compounding of drug products is appropriate and lawful, but these criteria expressly do not apply to radiopharmaceuticals. The Nuclear Pharmacy Compounding Practice Committee, a group of nuclear pharmacists convened by the American Pharmaceutical Association, developed the Nuclear Pharmacy Compounding Guidelines to establish a set of principles and guidelines for good radiopharmaceutical compounding practice. The intent of the new document is to provide guidance on radiopharmaceutical compounding practices that have evolved over the last 2 decades and to place them in an appropriate regulatory framework in accordance with previous enforcement policies and guidelines issued by the U.S. Food and Drug Administration (FDA) regarding the exemption of certain pharmacy practices from enforcement of adulteration, misbranding, and new drug requirements. CONCLUSION: The Nuclear Pharmacy Compounding Guidelines, recently released by APhA, is the first official document that provides realistic and practical compounding guidance for nuclear pharmacists. Even though the United States Court of Appeals for the Ninth Circuit recently ruled section 503A of the FD&C Act to be invalid in its entirety, and the Supreme Court upheld that ruling, the compliance policy guides issued by FDA in March 1992 and revised in May 2002 maintain guiding principles on pharmacy compounding similar to those stated in section 503A of the FD&C Act. The Nuclear Pharmacy Compounding Practice Committee is optimistic that the practical information contained in the Guidelines will assist state boards of pharmacy, FDA, and the United States Pharmacopeial Convention in setting appropriate standards for nuclear pharmacy compounding practice that will ensure the continued availability of high-quality compounded radiopharmaceuticals at reasonable cost.