Preparation and Characterization of Amorphous Solid Dispersions for the Solubilization of Fenretinide

Abstract

Fenretinide (4-HPR), a retinoid derivative, has shown high antitumor activity, a low toxicological profile, and no induction of resistance. Despite these favorable features, the variability in oral absorption due to its low solubility combined with the high hepatic first pass effect strongly reduce clinical outcomes. To overcome the solubility and dissolution challenges of poorly water-soluble 4-HPR, we prepared a solid dispersion of the drug (4-HPR-P5) using a hydrophilic copolymer (P5) previously synthesized by our team as the solubilizing agent. The molecularly dispersed drug was obtained by antisolvent co-precipitation, an easy and up-scalable technique. A higher drug apparent solubility (1134-fold increase) and a markedly faster dissolution were obtained. In water, the colloidal dispersion showed a mean hydrodynamic diameter of 249 nm and positive zeta potential (+41.3 mV), confirming the suitability of the formulation for intravenous administration. The solid nanoparticles were also characterized by a high drug payload (37%), as was also evidenced by a chemometric-assisted Fourier transform infrared spectroscopy (FTIR) investigation. The 4-HPR-P5 exhibited antiproliferative activity, with IC50 values of 1.25 and 1.93 µM on IMR-32 and SH-SY5Y neuroblastoma cells, respectively. Our data confirmed that the 4-HPR-P5 formulation developed herein was able to increase drug apparent aqueous solubility and provide an extended release over time, thus suggesting that it represents an efficient approach to improve 4-HPR bioavailability.

Keywords: Fenretinide; co-precipitation; drug delivery; lipophilic drugs; nanoparticles; neuroblastoma; solubilization.

Scheme 1

Synthetic pathway to prepare 4-HPR-P5 NPs.

Figure 1

FTIR spectra of 4-HPR-P5 NPs (green line), P5 (red line), and pristine 4-HPR (blue line) for easier comparison.

Figure 2

PCA results, represented as a score plot (PC1 vs. PC2).

Figure 3

Potentiometric titration of 4-HPR-P5 (red line); first derivative (dpH/dV) of the titration curve (purple line).

Figure 4

Buffer capacity curves of P5 and 4-HPR-P5 NPs.

Figure 5

Average buffer capacity of P5, 4-HPR-P5, and PEI-b 25 kD.

Figure 6

DSC thermograms of raw 4-HPR, P5, 4-HPR-P5 physical mixture, and 4-HPR-P5 NPs.

Figure 7

(a) Representative size distribution of 4-HPR-P5 NPs and (b) representative zeta potential obtained by dissolving 2 mg/mL of nanoparticles in water at 25 °C.

Figure 8

CR% of 4-HPR from NPs and from its suspension at pH 7.4, monitored for 72 h.

Figure 9

Linear regression of Weibull mathematical kinetic model with the related equation and R² value.

Figure 10

Dose- and time-dependent cytotoxicity activity of P5, 4-HPR, and 4-HPR-P5 NPs at 24 h (a), 48 h (b), and 72 h (c) in SH-SY5Y cells. Concentration values reported on the x-axis refer to 4-HPR, while the concentrations used for P5 and 4-HPR-P5 NPs can be derived from Table 2. White columns: control; yellow columns: P5; green columns: free 4-HPR; and checkered columns: 4-HPR-P5 NPs. Significance refers to control (p > 0.05 ns; p < 0.05 *; p < 0.01 **; p < 0.001 ***).

Figure 10

Dose- and time-dependent cytotoxicity activity of P5, 4-HPR, and 4-HPR-P5 NPs at 24 h (a), 48 h (b), and 72 h (c) in SH-SY5Y cells. Concentration values reported on the x-axis refer to 4-HPR, while the concentrations used for P5 and 4-HPR-P5 NPs can be derived from Table 2. White columns: control; yellow columns: P5; green columns: free 4-HPR; and checkered columns: 4-HPR-P5 NPs. Significance refers to control (p > 0.05 ns; p < 0.05 *; p < 0.01 **; p < 0.001 ***).

Figure 11

Dose- and time-dependent cytotoxicity activity of P5, 4-HPR, and 4-HPR-P5 NPs at 24 h (a), 48 h (b), and 72 h (c) in IMR-32 cells. Concentration values reported on the x-axis refer to 4-HPR, while the concentrations used for P5 and 4-HPR-P5 NPs can be derived from Table 2. White columns: control; yellow columns: P5; green columns: free 4-HPR; and checkered columns: 4-HPR-P5 NPs. Significance refers to control (p > 0.05 ns; p < 0.01 **; p < 0.001 ***).

Figure 11

Dose- and time-dependent cytotoxicity activity of P5, 4-HPR, and 4-HPR-P5 NPs at 24 h (a), 48 h (b), and 72 h (c) in IMR-32 cells. Concentration values reported on the x-axis refer to 4-HPR, while the concentrations used for P5 and 4-HPR-P5 NPs can be derived from Table 2. White columns: control; yellow columns: P5; green columns: free 4-HPR; and checkered columns: 4-HPR-P5 NPs. Significance refers to control (p > 0.05 ns; p < 0.01 **; p < 0.001 ***).

Figure 12

Dose-dependent cytotoxicity activity of P5 at 24 h (blue), 48 h (orange), and 72 h (red) in IMR-32 cells (a) and SH-SY5Y cells (b) in the range 0.013–1.96 µM.

Figure 13

Dose-dependent cytotoxicity activity of 4-HPR at 24 h (blue), 48 h (orange), and 72 h (red) in IMR-32 cells (a) and SH-SY5Y cells (b) in the range 0.1–5 µM (a) and 0.1-15 µM (b).

Figure 14

Dose-dependent cytotoxicity activity of 4-HPR-P5 NPs at 24 h (blue), 48 h (orange), and 72 h (red) in IMR-32 cells (a) and SH-SY5Y cells (b) in the range 0.013–1.96 µM.