Establishment and comparison of three novel methods for the determination of the photodynamic therapy agent 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) in human serum

Pre-clinical compartmental pharmacokinetic modeling of 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) as a photosensitizer in rat plasma by validated HPLC method

A second-generation chlorin-based photosensitizer, 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) has shown tremendous therapeutic potential in clinical trials in the treatment of esophageal cancer. Herein, we have developed and validated a bioanalytical method for estimation of HPPH in rat plasma using High Performance Liquid Chromatography (HPLC) with a photo diode array (PDA) detector. The method was applied for carrying out pharmacokinetic study of HPPH. Further pharmacokinetic modeling was carried out to understand the compartment kinetics of HPPH. The developed method was fully validated as per the United States Food and Drug Administration (US-FDA) guidelines for bioanalytical method validation. The linearity of the method was in the range of 250-8000 ng mL-1, and the plasma recovery was found to be 70%. Pharmacokinetic parameters were evaluated and compared via non-compartment analysis and compartment modeling after the intravenous (i.v.) bolus administration in rats using Phoenix WinNonlin 8.0 (Certara™, USA). From the obtained results, we hypothesize that the HPPH complies with two compartmental pharmacokinetic model. Furthermore, it was observed that HPPH has the rapid distribution from the central compartment to peripheral compartment along with slow elimination from peripheral compartment.

Evaluation on Short-Term Therapeutic Effect of 2 Porphyrin Photosensitizer-Mediated Photodynamic Therapy for Esophageal Cancer

Purpose:

To analyze and study the short-term therapeutic effects and main adverse effects of 2 Porphyrin photosensitizer-mediated photodynamic therapy for esophageal cancer.

Methods:

We apply the hematoporphyrin derivative and hematoporphyrin injection produced by different manufacturers at different periods as photosensitizers in therapy of 79 esophageal cancer cases, with the administration dosage of 5 mg/kg and intravenous drip 24 hours before irradiation. We apply the gold vapor laser and semiconductor laser, respectively, as treatment light source, with the power density of 100 to 300 mW/cm² and energy density of 100 to 300 J/cm². After treatment for 1 to 4 sessions, we evaluate the short-term therapeutic effects as complete response, partial response, minor response, or no change, and then make comparative study on therapeutic effects and adverse effects.

Results:

There were 47 patients in hematoporphyrin derivative group, including 3 (6.4%) patients with complete response, 31 (66.0%) patients with partial response, 10 (21.3%) patients with minor response, and 3 (6.4%) patients with no change. The dysphagia score was reduced from 2.53 (1.16) before treatment to 1.32 (1.20; P < .01) after treatment. There were 32 patients in the hematoporphyrin injection group, including 3 (9.4%) patients with complete response, 19 (59.4%) patients with partial response, 6 (18.8%) patients with minor response, and 4 (12.5%) patients with no change. The dysphagia score was reduced from 2.41 (1.13) before treatment to 1.18 (0.99; P < .01) after treatment. The dysphagia scores of 2 groups after treatment were significantly reduced compared to those before treatment. Both groups did not display serious adverse effect.

Conclusions:

Two porphyrin photosensitizers in treatment of esophageal cancer at different clinical stages all had good effect with similar therapeutic effect, mild adverse effect, and good tolerance, which implies it is a preferable palliative therapy means.

Population pharmacokinetic modeling and simulation of HPPH in Chinese patients with esophageal carcinoma

1. 2-[1-Hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH), a second-generation photosensitizer, has been widely employed in photodynamic therapy (PDT) for the treatment of malignant lesions. The objective of this study was to characterize the pharmacokinetics of HPPH in Chinese patients using a population pharmacokinetic (PopPK) approach.2. For the first time, a PopPK model of HPPH for Chinese (n = 20) was developed (registration number: CTR20160425). The pharmacokinetics of HPPH was described by a three-compartment model with linear elimination. Through the stepwise addition (p < 0.05) and backward elimination (p < 0.001) approach, fat-free mass (FFM) was identified to be the most significant covariate and V₁ increased with FFM. Visual predictive check (VPC) was employed for the evaluation of the final model. Subsequent full covariate analysis indicated that FFM has considerable impact (∼30%) on HPPH exposure and fat mass also has a modest (∼25%) impact.3. The simulations suggested that a dose adjustment of HPPH may be necessary for Chinese and the dose of 3 mg/m² should be appropriate. HPPH exposure increases with fat mass while being inversely related to FFM. HPPH-PDT for overweight patients should be monitored with more caution and PDT conditions should be optimized if necessary.