Antitumor efficacy and local distribution of doxorubicin via intratumoral delivery from polymer millirods

Nanoparticle-mediated combination chemotherapy and photodynamic therapy overcomes tumor drug resistance

Tumor drug resistance significantly limits the success of chemotherapy in the clinic. Tumor cells utilize multiple mechanisms to prevent the accumulation of anticancer drugs at their intracellular site of action. In this study, we investigated the anticancer efficacy of doxorubicin in combination with photodynamic therapy using methylene blue in a drug-resistant mouse tumor model. Surfactant-polymer hybrid nanoparticles formulated using an anionic surfactant, Aerosol-OT (AOT), and a naturally occurring polysaccharide polymer, sodium alginate, were used for synchronized delivery of the two drugs. Balb/c mice bearing syngeneic JC tumors (mammary adenocarcinoma) were used as a drug-resistant tumor model. Nanoparticle-mediated combination therapy significantly inhibited tumor growth and improved animal survival. Nanoparticle-mediated combination treatment resulted in enhanced tumor accumulation of both doxorubicin and methylene blue, significant inhibition of tumor cell proliferation, and increased induction of apoptosis. These data suggest that nanoparticle-mediated combination chemotherapy and photodynamic therapy using doxorubicin and methylene blue has significant therapeutic potential against drug-resistant tumors.

Intratumoral delivery of beta-lapachone via polymer implants for prostate cancer therapy

PURPOSE

beta-Lapachone (ARQ 501, a formulation of beta-lapachone complexed with hydroxypropyl-beta-cyclodextrin) is a novel anticancer agent with selectivity against prostate cancer cells overexpressing the NAD(P)H:quinone oxidoreductase-1 enzyme. Lack of solubility and an efficient drug delivery strategy limits this compound in clinical applications. In this study, we aimed to develop beta-lapachone-containing polymer implants (millirods) for direct implantation into prostate tumors to test the hypothesis that the combination of a tumor-specific anticancer agent with site-specific release of the agent will lead to significant antitumor efficacy.

EXPERIMENTAL DESIGN

Survival assays in vitro were used to test the killing effect of beta-lapachone in different prostate cancer cells. beta-Lapachone release kinetics from millirods was determined in vitro and in vivo. PC-3 prostate tumor xenografts in athymic nude mice were used for antitumor efficacy studies in vivo.

RESULTS

beta-Lapachone killed three different prostate cancer cell lines in an NAD(P)H:quinone oxidoreductase-1-dependent manner. Upon incorporation of solid-state inclusion complexes of beta-lapachone with hydroxypropyl-beta-cyclodextrin into poly(D,L-lactide-co-glycolide) millirods, beta-lapachone release kinetics in vivo showed a burst release of approximately 0.5 mg within 12 hours and a subsequently sustained release of the drug ( approximately 0.4 mg/kg/d) comparable with that observed in vitro. Antitumor efficacy studies showed significant tumor growth inhibition by beta-lapachone millirods compared with controls (P < 0.0001; n = 10 per group). Kaplan-Meier survival curves showed that tumor-bearing mice treated with beta-lapachone millirods survived nearly 2-fold longer than controls, without observable systemic toxicity.

CONCLUSIONS

Intratumoral delivery of beta-lapachone using polymer millirods showed the promising therapeutic potential for human prostate tumors.

A simple HPLC method for doxorubicin in plasma and tissues of nude mice

Doxorubicin is a cytotoxic anthracycline that has been used for the treatment of several malignancies. Several HPLC methods have been reported for the quantification of doxorubicin in biological samples. Tissue matrix effect and sample size requirements, however, have been remaining issues for simple and easy-to-adapt analytical methods in small animal experiments. The present study established a simple HPLC method for doxorubicin in plasma and tissues (tumor, heart, spleen, liver, gastrointestinal tract, brain, lung, and kidney) of nude mice. Our method required a small sample volume (100 microL plasma and 10 mg tissue), which made it possible to use each blank tissue for calibration curves. The limit of quantification was 25 ng/mL in plasma and 0.1 to 0.4 microg/mg in other tissues with recovery rates ranging from 52.4 to 95.2%. The linearity, accuracy and precision in all tissues, except gastrointestinal tract (GIT), were found to be acceptable in the range of 25-2000 ng/mL plasma and 0.1-4 ng/mg tissue. This method was used successfully to determine the drug concentration in plasma and tissues of human tumor xenograft-bearing nude mice given intratumoral doxorubicin in a polymeric drug delivery system designed for sustained release. In conclusion, the present method may be useful as a simple and easy-to-adapt, yet, sensitive analytical method of doxorubicin for plasma and tissue pharmacokinetic studies in small animals such as nude mice.

Drug-eluting polymer implants in cancer therapy

BACKGROUND

Drug-eluting polymer implants present a compelling parenteral route of administration for cancer chemotherapy. With potential for minimally invasive, image-guided placement and highly localized drug release, these delivery systems are playing an increasingly important role in cancer management. This is particularly true as the use of labile proteins and other bioactive molecules is likely to increase in the upcoming years.

OBJECTIVE

In this review, we present the current trends in the application of Pre-formed and in situ-forming systems as drug-eluting implants for cancer chemotherapy.

METHODS

We outline the clinically available options as well as up-and-coming technologies and their advantages and challenges. We also describe ongoing related innovations with image-guided drug delivery, mathematical modeling of implanted delivery systems and implanted drug delivery in combination with other therapies.

RESULTS/CONCLUSION

Whether used alone or combined with other minimally invasive procedures, drug-eluting polymeric implants will play a significant role in the future of cancer management.

Model simulation and experimental validation of intratumoral chemotherapy using multiple polymer implants

Radiofrequency ablation has emerged as a minimally invasive option for liver cancer treatment, but local tumor recurrence is common. To eliminate residual tumor cells in the ablated tumor, biodegradable polymer millirods have been designed for local drug (e.g., doxorubicin) delivery. A limitation of this method has been the extent of drug penetration into the tumor (<5 mm), especially in the peripheral tumor rim where thermal ablation is less effective. To provide drug concentration above the therapeutic level as needed throughout a large tumor, implant strategies with multiple millirods were devised using a computational model. This dynamic, 3-D mass balance model of drug distribution in tissue was used to simulate the consequences of various numbers of implants in different locations. Experimental testing of model predictions was performed in a rabbit VX2 carcinoma model. This study demonstrates the value of multiple implants to provide therapeutic drug levels in large ablated tumors.

Effect of formulation parameters on 2-methoxyestradiol release from injectable cylindrical poly(DL-lactide-co-glycolide) implants

The objective of this study was to investigate the potential of various formulation strategies to achieve 1-month continuous (improved) release of the novel anti-cancer drug, 2-methoxyestradiol (2-ME), from injectable cylindrical poly(DL-lactide-co-glycolide) (PLGA) implants. PLGA implants were prepared by a solvent extrusion method. PLGA 50:50 (M(w)=51 kDa, end group=lauryl ester) (PLGA-lauryl ester) implants loaded with 3-30 wt% 2-ME exhibited a pronounced lag phase (i.e., corresponding to induction time to polymer mass loss) and triphasic release profile. Incorporation of 5 wt% hydroxypropyl-beta-cyclodextrin (HP-beta-CD) (approximately 57% release after 28 days) or Pluronic F127 (approximately 42% release after 28 days) in PLGA-lauryl ester implants reduced the lag-phase and improved the drug release moderately over a period of 28 days. The formation and the incorporation of a 2-ME/polyethylene glycol (PEG) 8000 solid dispersion in PLGA-lauryl ester implants further increased drug release (approximately 21% and 73% release after 1 and 28 days, respectively), attributable to improved drug solubility/dissolution, higher matrix porosity, and accelerated polymer degradation. Blending of PLGA 50:50 (M(w)=24 kDa, end group=COOH) (PLGA-COOH) with the PLGA-lauryl ester also provided moderate enhancement of 2-ME release over a period of 28 days. PLGA-COOH (M(w)=24 kDa) implants with 3-5% w/w pore-forming MgCO(3) exhibited the most desirable drug release among all the formulations tested, and, demonstrated 1-month slow and continuous in vitro release of approximately 80% 2-ME after a minimal initial burst. Hence, these formulation approaches provide several possible avenues to improve release rates of the hydrophobic drug, 2-ME, from PLGA for future application in regional anti-cancer therapy.

Modeling doxorubicin transport to improve intratumoral drug delivery to RF ablated tumors

A mathematical model of drug transport provides an ideal strategy to optimize intratumoral drug delivery implants to supplement radiofrequency (RF) ablation for tumor treatment. To simulate doxorubicin transport in non-ablated and ablated liver tumors, a one-dimensional, cylindrically symmetric transport model was generated using a finite element method (FEM). Parameters of this model, the diffusion (D) and elimination (gamma) coefficients for doxorubicin, were estimated using drug distributions measured 4 and 8 days after placing biodegradable implants in non-ablated and ablated rabbit VX2 liver carcinomas. In non-ablated tumor, values of diffusion and elimination parameters were 25% and 94% lower than normal liver tissue, respectively. In ablated tumor, diffusion near the ablation center was 75% higher than non-ablated tumor but decreased to the non-ablated tumor value at the ablation periphery. Drug elimination in ablated tumor was zero for the first four days, but by day 8 returned to 98% of the value for non-ablated tumor. Three-dimensional (3-D) simulations of drug delivery from implants with and without RF thermal ablation underscore the benefit of using RF ablation to facilitate local drug distribution. This study demonstrates the use of computational modeling and optimal parameter estimation to predict local drug pharmacokinetics from intratumoral implants after ablation.

A mechanistic model of controlled drug release from polymer millirods: Effects of excipients and complex binding

The incorporation of different cyclodextrin (CD) excipients such as HPbeta-CD, beta-CD, gamma-CD or alpha-CD into polymer millirods for complexing beta-lapachone (beta-lap), a potent anti-cancer drug, significantly improved the drug release kinetics with various drug release patterns. However, such a complex system requires a mechanistically based model in order to provide a quantitative understanding of the many molecular events and processes that are essential for the rational development of millirod implants. This study focuses on mathematical modeling of drug release from PLGA cylindrical millirods. This millirod system incorporates multiple components: a PLGA matrix; excipient in free and complex forms; drug in free, bound, and crystalline forms. The model characterizes many dynamic transport and complexation processes that include radial diffusion, excipient complexation and crystalline drug dissolution. Optimal estimates of the model parameters were obtained by minimizing the difference between model simulation and experimentally measured drug release kinetics. The effects of different drug loadings on the drug release rate were simulated and compared with other data to validate this model. Whereas our model can simulate all the experimental data, the Higuchi model can simulate only some of them. Furthermore, our model incorporates mechanisms by which the processes underlying drug release from a polymer matrix can be quantitatively analyzed. These processes include drug entrapment/dissolution in the matrix, drug recrysallization, and supersaturation. This modeling study shows that complex binding capacity, which affects drug initial conditions, drug-polymer interactions, and bound drug behavior in aqueous solution, is crucial in controlling drug release kinetics.