The Challenging Pharmacokinetics of Mitotane: An Old Drug in Need of New Packaging.

Adrenocortical carcinoma (ACC) is a malignant tumor originating from the adrenal gland cortex with a heterogeneous but overall dismal prognosis in advanced stages. For more than 50 years, mitotane has remained a cornerstone for the treatment of ACC as adjuvant and palliative therapy. It has a very poor aqueous solubility of 0.1 mg/l and high partition coefficient in octanol/water (log P) value of 6. The commercially available dosage form is 500 mg tablets (Lysodren®). Even at doses up to 6 g/day (12 tablets in divided doses) for several months, > 50% patients do not achieve therapeutic plasma concentration > 14 mg/l due to poor water solubility, large volume of distribution and inter/intra-individual variability in bioavailability. This article aims to give a concise update of the clinical challenges associated with the administration of high-dose mitotane oral therapy which encompass the issues of poor bioavailability, difficult-to-predict pharmacokinetics and associated adverse events. Moreover, we present recent efforts to improve mitotane formulations. Their success has been limited, and we therefore propose an injectable mitotane formulation instead of oral administration, which could bypass many of the main issues associated with high-dose oral mitotane therapy. A parenteral administration of mitotane could not only help to alleviate the adverse effects but also circumvent the variable oral absorption, give better control over therapeutic plasma mitotane concentration and potentially shorten the time to achieve therapeutic drug plasma concentrations considerably.

Mitotane as tablet form is currently the standard treatment for adrenocortical carcinoma. It has been used for 5 decades but suffers from highly variable responses in patients, subsequent adverse effects and overall lower response rate. This can be fundamentally linked to the exceedingly poor water solubility of mitotane itself. In terms of enhancing water solubility, a few research groups have attempted to develop better formulations of mitotane to overcome the issues associated with tablet dosage form. However, the success rate was limited, and these formulations did not make it into the clinics. In this article, we have comprehensively reviewed the properties of these formulations and discuss the reasons for their limited utility. Furthermore, we discuss a recently developed mitotane nanoformulation that led us to propose a novel approach to mitotane therapy, where intravenous delivery supplements the standard oral administration. With this article, we combine the current state of knowledge as a single piece of information about the various problems associated with the use of mitotane tablets, and herein we postulate the development of a new injectable mitotane formulation, which can potentially circumvent the major problems associated to mitotane's poor water solubility.

An Advanced Computational Evaluation for the Most Biologically Active Enantiomers of Chiral Anti-Cancer Agents.

BACKGROUND: Cancer is a very dangerous disease whose treatment can be improved by removing the factors that cause side effects if the drugs prescribed for cancer are chiral in nature. OBJECTIVES: A computational evaluation for the most biologically active enantiomeric form of chiral drugs attacking the DNA of the cell, was made for the first time, and compared with the experimental work done by others previously. METHODS: All the enantiomeric structures of the drugs taken in the present study were obtained using Marvin sketch, and the structure of DNA to be docked with enantiomers, was obtained from the protein data bank. After that, all the enantiomers of the chiral drugs were docked with DNA one by one for the evaluation of the most biologically active enantiomeric form. RESULTS: The docking study showed that the different enantiomers interacted with DNA differently because of having different arrangements of atoms/groups. The binding affinity of one of the two enantiomeric forms was higher than that of another. CONCLUSION: R-methotrexate for breast cancer; R-mitotane for adrenocortical cancer; R-duvelisib for blood cancer, and S-irinotecan for colon cancer would be a suitable drug with less toxicity as well as other side effects.

A simplified method for therapeutic drug monitoring of mitotane by gas chromatography-electron ionization-mass spectrometry.

Mitotane is a key drug for the treatment of adrenal cortical carcinoma. Due to its narrow therapeutic window, 14-20 µg/mL, monitoring its concentration is crucially important. In this study, a simplified method for measuring mitotane in plasma using gas chromatography-electron ionization-mass spectrometry (GC-EI-MS) was developed. Through deproteination and liquid-liquid extraction, mitotane and an internal standard (IS) were extracted from plasma samples. GC-EI-MS yielded retention times of 8.2 and 8.7 min, for mitotane and the IS, respectively, with a total run time of 12 min. Selectivity and intra-/inter-batch accuracy and precision analyses provided a lower limit of quantification of 0.25 µg/mL, and a calibration curve between 0.25 and 40 µg/mL had good linearity (coefficient of determination = 0.992). The matrix effect factor and percent recovery of the method had good precision. Additionally, long-term sample stability was observed below 4°C. In a clinical setting, mitotane levels in plasma from an adrenal cortical carcinoma patient were within calibration range. Therefore, this simplified method can be applied to routine therapeutic drug monitoring of mitotane, which may contribute to improved treatment of adrenal cortical carcinoma.

A Micellar Mitotane Formulation with High Drug-Loading and Solubility: Physico-Chemical Characterization and Cytotoxicity Studies in 2D and 3D In Vitro Tumor Models.

Adrenocortical carcinoma (ACC) is a rare tumor and prognosis is overall poor but heterogeneous. Mitotane (MT) has been used for treatment of ACC for decades, either alone or in combination with cytotoxic chemotherapy. Even at doses up to 6 g per day, more than half of the patients do not achieve targeted plasma concentration (14-20 mg L-1 ) even after many months of treatment due to low water solubility, bioavailability, and unfavorable pharmacokinetic profile. Here a novel MT nanoformulation with very high MT concentrations in physiological aqueous media is reported. The MT-loaded nanoformulations are characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and powder X-ray diffraction which confirms the amorphous nature of the drug. The polymer itself does not show any cytotoxicity in adrenal and liver cell lines. By using the ACC model cell line NCI-H295 both in monolayers and tumor cell spheroids, micellar MT is demonstrated to exhibit comparable efficacy to its ethanol solution. It is postulated that this formulation will be suitable for i.v. application and rapid attainment of therapeutic plasma concentrations. In conclusion, the micellar formulation is considered a promising tool to alleviate major drawbacks of current MT treatment while retaining bioactivity toward ACC in vitro.

Therapeutic drug monitoring of mitotane: Analytical assay and patient follow-up.

Adrenocortical carcinoma (ACC) is an aggressive malignancy of the adrenal gland. Mitotane (o,p'-DDD) is the most effective chemotherapy for ACC. According to the literature, mitotane plasma trough concentrations within 14-20 mg L-1 are correlated with a higher response rate with acceptable toxicity. Therapeutic drug monitoring (TDM) of mitotane is therefore recommended. The aim of this study was to propose a robust and simple method for mitotane quantification in plasma. The validation procedures were based on international guidelines. Sample preparation consisted of a single protein precipitation with methanol using 100 µL of plasma. The supernatant was submitted to liquid chromatography coupled with ultra-violet detection at 230 nm. Mitotane retention time was 7.1 min. The limit of detection was 0.1 mg L-1 and the limit of quantification was 0.78 mg L-1 . The assay demonstrated a linear range of 0.78-25 mg L-1 with correlation coefficients (r2 ) at 0.999. Inter- and intra-assay precision was <4.85%. Evaluation of accuracy showed a deviation <13.69% from target concentration at each quality control level. This method proved easy and rapid to perform mitotane TDM and required a small volume of sample. It was successfully applied to routine TDM in our laboratory.

The adrenal specific toxicant mitotane directly interacts with lipid membranes and alters membrane properties depending on lipid composition.

Mitotane (o,p'.-DDD) is an orphan drug approved for the treatment of adrenocortical carcinoma. The mechanisms, which are responsible for this activity of the drug, are not completely understood. It can be hypothesized that an impact of mitotane is mediated by the interaction with cellular membranes. However, an interaction of mitotane with (lipid) membranes has not yet been investigated in detail. Here, we characterized the interaction of mitotane and its main metabolite o,p'-dichlorodiphenyldichloroacetic acid (o,p'-DDA) with lipid membranes by applying a variety of biophysical approaches of nuclear magnetic resonance, electron spin resonance, and fluorescence spectroscopy. We found that mitotane and o,p'-DDA bind to lipid membranes by inserting into the lipid-water interface of the bilayer. Mitotane but not o,p'-DDA directly causes a disturbance of bilayer structure leading to an increased permeability of the membrane for polar molecules. Mitotane induced alterations of the membrane integrity required the presence of phosphatidylethanolamine and/or cholesterol. Collectively, our data for the first time characterize the impact of mitotane on the lipid membrane structure and dynamics, which may contribute to a better understanding of specific mitotane effects and side effects.

Lipoprotein-Free Mitotane Exerts High Cytotoxic Activity in Adrenocortical Carcinoma.

CONTEXT: Mitotane (o,p'-DDD), the only approved drug for advanced adrenocortical carcinoma (ACC), is a lipophilic agent that accumulates into circulating lipoprotein fractions and high-lipid-containing tissues. OBJECTIVE: The aim of our study was to evaluate the in vivo and in vitro biological implication of serum lipoproteins on pharmacological action of mitotane. Distribution and concentration of mitotane were studied in plasma and adrenal tissue samples from mitotane-treated patients. The effect of lipoprotein-bound or lipoprotein-free (LP-F) mitotane was analyzed on proliferation and apoptosis of human adrenocortical H295R cells. A retrospective study of patients with ACC treated or not with statins was also performed. RESULTS: o,p'-DDD distribution among very low-density lipoprotein, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and LP-F fractions obtained after plasma ultracentrifugation of 23 of mitotane-treated patients was widely distributed in each subfraction. A positive correlation was observed between mitotane levels in plasma and in LDL, HDL, but also LP-F compartment. Intratumor o,p'-DDD concentrations in five ACC samples of mitotane-treated patients were found to be independent of cholesterol transporter expression, scavenger receptors, and LDL receptors. In vitro studies showed significant higher antiproliferative and proapoptotic effects and higher cell and mitochondrial uptake of mitotane when H295R cells were grown in LP-F medium. Finally, retrospective study of an ACC cohort of 26 mitotane-treated patients revealed that statin therapy was significantly associated with a higher rate of tumor control. CONCLUSIONS: Altogether, our in vitro and in vivo studies provided compelling evidence for a greater efficacy of LP-F mitotane. Patients with ACC may thus benefit from therapeutic strategies that aim to increase LP-F mitotane fraction.

Characterization of mitotane (o,p'-DDD)--cyclodextrin inclusion complexes: phase-solubility method and NMR.

Mitotane (o,p'-dichlorodimethyl dichloroethane [o,p'-DDD]) is used for the treatment of adrenocortical cancer and occasionally Cushing's syndrome. This drug is very poorly soluble in water, and following oral administration, approximately 60% of the dose is recovered in the feces unaltered. The preparation of a soluble formulation (i.e. by complexation with cyclodextrins) with improved bioavailability is the aim of this work. The inclusion of mitotane in methyl-ß-cyclodextrins was studied using both phase-solubility methods and NMR experiments. To elucidate the inclusion mechanism, o,p'-DDD was compared to its regioisomer (i.e. p,p'-DDD). It was demonstrated that two dimethyl-ß-cyclodextrins (DMßCD) can complex with the aromatic rings. From the phase-solubility diagrams, we observe that both cases are very different: K(1:1) is between 37 000 and 85 000 mol.l(-1), whereas K(1:2) is between 5.3 and 32 mol.l(-1). The NMR experiments confirmed the inclusion but it also gave an insight into the kinetics of the dissociation: the ortho-chloro moiety is in slow exchange on the NMR time scale, whereas the para-chloro moiety is in fast exchange rate.

Development of mitotane lipid nanocarriers and enantiomers: two-in-one solution to efficiently treat adreno-cortical carcinoma.

Adrenocortical carcinoma (ACC) is a rare but aggressive malignancy with a poor prognosis. Treatment options for advanced ACC are limited. Indeed, radical tumor resection can lead to local or metastatic recurrence, and mitotane (Lysodren(®)), the only recognized adrenolytic drug, offers modest response rates, notably due to some of its physico-chemical and pharmacological properties (i.e. hydrophobicity, low bioavailability). Meantime, high cumulative doses of Lysodren(®) usually cause systemic toxicities. To reduce adverse health effects, the search of safe and efficient mitotane nano-formulations as well as the full characterization and testing of its enantiomers can represent valuable therapeutic options. Interestingly, recent investigations showed that solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) could considerably improve the efficacy of mitotane (i.e. enhanced solubility and bioavailability, progressive release of the loaded drug into blood and targeted tissues) as well as its safety (i.e. lower toxicity, higher biocompatibility). These two nano-carriers for mitotane delivery and targeting are of particular interest over other polymeric particles (i.e. low-cost, efficient and simple scaling to an industrial production level following green methods). Besides, emerging studies suggested that the S-(-)- mitotane is more potent than the R-(+)-mitotane for ACC treatment. Therefore, the production of pure and active S-(-)-mitotane might offer synergic or additive benefits for ACC patients when combined to solid lipid-based nanocarriers. In this review, we first provide an updated overview of the ACC disease before emphasizing on the promising mitotane drug nano-systems, as well as on the separation, purification and production of single mitotane enantiomer using state-of-art chromatographic-based methods.

Structural requirements for mitotane activity: development of analogs for treatment of adrenal cancer.

AIM: Mitotane is used in adrenal cancer as adjuvant therapy, monotherapy or combined with other cytotoxic agents in advanced disease, but only 30% of patients respond. The aim of this study was to define the structural requirements for drug activity and to develop analogs with improved adrenalytic action. MATERIALS AND METHODS: Nine analogs of [1-(2-chlorophenyl)-1-(4-chlorophenyl)-2,2dichloroethane] (o,p'-DDD) were tested by measuring suppression of cortisol secretion and the presence of inflammatory changes in the dog adrenal and inhibition of cell proliferation and cortisol production by NCI-H295 human adrenal cancer cells. RESULTS: In addition to mitotane, o,p'-DDClBr and o,p'-DDBr(2), were active in vitro and in vitro: Their effects were comparable to that of o,p'-DDD when tested at 50 µM concentration, but o,p'DDBr(2) was significantly more active at the lower 20 µM concentration. CONCLUSION: A dihalogenated methine carbon is required for adrenalytic activity. A change in the aromatic portion of the mitotane molecule causes loss of activity. Because of its greater activity at lower concentrations, o,p'-DDBr(2) has potential application in the treatment of patients with adrenal cancer.

Mitotane treatment for adrenocortical carcinoma: an overview.

Adrenocortical carcinoma (ACC) is a rare aggressive endocrine neoplasm characterized by a 5-year survival of less than 50%. Due to the widespread use of imaging techniques in clinics, ACC is increasingly recognized as an incidentally discovered tumor. Mostly characterized by poor prognosis, ACC is often diagnosed at an advanced stage of disease. Early diagnosis is uncommon; when diagnosed, ACCs are usually large and have invaded adjacent organs, even if metastatic spread to distant sites can be absent. Complete surgical resection is the only potentially curative treatment for patients with localized disease; however, due to a recurrence rate of 50-70% after apparent radical surgery, there is a strong rationale for a concomitant systemic treatment. Adrenolytic therapy with mitotane (o,p>-DDD), administered alone or in combination with others antineoplastic agents, is the primary treatment for patients with advanced ACC and is increasingly used also in an adjuvant setting, even if controversy exists on this issue due to the limitations of the available literature. Despite being in use for many years, the rarity of ACC precluded the organization of randomized trials; thus, many areas of uncertainty and controversy remain regarding the role of this old drug in the clinical management of patients with ACC. The purpose of this paper is to review the current evidence on mitotane treatment in patients with advanced disease and in ACC patients after complete surgical resection as adjuvant treatment.

Enhancement of dissolution rate of mitotane and warfarin prepared by using microemulsion systems.

Micronization is the most effective way to enhance the dissolution rate of poorly water-soluble drugs and bioavailability in human body. Microemulsion systems were applied to micronize mitotane and warfarin by cooling method and solvent diffusion process. The triangle phase diagram of the ternary benzyl alcohol+sodium dodecyl sulfate (SDS)+water system was investigated at six different temperatures to determine an appropriate operational microemulsion regime for crystallization. The particle sizes of mitotane and warfarin re-crystallized from microemulsion systems were greatly reduced (to ∼1 µm) compared with that of the commercial ones. Consequently, the dissolution rate coefficients of re-crystallized mitotane and warfarin were significantly improved by, respectively, 7.5 and 13.3 times larger than that of the commercial ones. The crystal structures of re-crystallized mitotane and warfarin were the same as the commercial ones based on the XRD and DSC measurements. In addition, it is interesting to observe the variation of morphology of re-crystallized mitotane as a function of the composition of the SDS and the drug concentrations.

Chiral effects in adrenocorticolytic action of o,p'-DDD (mitotane) in human adrenal cells.

Adrenocortical carcinoma (ACC) is a rare malignant disease with poor prognosis. The main pharmacological choice, o,p'-DDD (mitotane), produces severe adverse effects. Since o,p'-DDD is a chiral molecule and stereoisomers frequently possess different pharmacokinetic and/or pharmacodynamic properties, we isolated the two o,p'-DDD enantiomers, (R)-(+)-o,p'-DDD and (S)-(-)-o,p'-DDD, and determined their absolute structures. The effects of each enantiomer on cell viability and on cortisol and dehydroepiandrosterone (DHEA) secretion in the human adrenocortical cell line H295R were assessed. We also assayed the o,p'-DDD racemate and the m,p'- and p,p'-isomers. The results show small but statistically significant differences in activity of the o,p'-DDD enantiomers for all parameters tested. The three DDD isomers were equally potent in decreasing cell viability, but p,p'-DDD affected hormone secretion slightly less than the o,p'- and m,p'-isomers. The small chiral differences in direct effects on target cells alone do not warrant single enantiomer administration, but might reach importance in conjunction with possible stereochemical effects on pharmacokinetic processes in vivo.

Synthesis of 2-(4-chlorophenyl)-2-(4-chloro-3-thiophenol)-1,1-dichloroethene (3-SH-DDE) via Newman-Kwart rearrangement - a precursor for synthesis of radiolabeled and unlabeled alkylsulfonyl-DDEs.

For the first time, a pathway for synthesis of 2-(4-chlorophenyl)-2-(4-chloro-3-thiophenol)-1,1-dichloroethene (3-SH-DDE), is presented. The compound is of particular interest as a precursor for synthesis of alkylsulfonyl-DDE containing different alkyl groups to discover structural activity relationships, and to promote synthesis of radiolabeled methylsulfonyl-DDE. 2-Chloro-5-methylphenol was first methylated and further oxidized to the corresponding benzoic acid. The acid was reduced to the corresponding aldehyde (4-chloro-3-methoxy benzaldehyde) via 4-chloro-3-methoxy-benzene methanol. A lead/aluminium bimetal system was used to carry out the reductive addition of tetrachloromethane to 4-chloro-3-methoxy benzaldehyde to obtain 2,2,2-trichloro-1-(4-chloro-3-methoxyphenyl)ethanol, the desired starting material to synthesize the DDT-analogue (2-(4-chlorophenyl)-2-(4-chloro-3-methoxy-phenyl)-1,1,1-trichloroethane). Elimination of hydrochloric acid and removal of the methyl group led to the 3-OH-DDE. The Newman-Kwart rearrangement was applied to convert 3-OH-DDE to 3-SH-DDE via the dimethylcarbamothioate derivative. 3-SH-DDE is then used as a precursor for the radiolabel synthesis. The overall yield to acquire 3-SH-DDE after 11 steps was 3%. The step with the lowest yield was the DDT-analog synthesis with a yield of 30%. All other step had a yield of >50%. 3-SH-DDE was methylated with (14)C-labeled iodomethane and oxidized by hydrogen peroxide to obtain 3-[(14)C]MeSO(2)-DDE in an overall yield of 30%.

Determination of chiral ratio of o,p-DDT and o,p-DDD pesticides on polysaccharides chiral stationary phases by HPLC under reversed-phase mode.

A simple and reliable HPLC method for the chiral resolution of o,p-DDT and o,p-DDD is described. The enantiomeric resolution of o,p-DDT and o,p-DDD has been achieved on Chiralpak AD-R, Chiralcel OD-R, and Chiralcel OJ-R chiral stationary phases. The mobile phases used were acetonitrile-water (50:50 [v/v]) and acetonitrile-2-propanol (50:50 [v/v]) at a flow rate of 1.0 mL/min. For both pesticides detection was done at 220 nm. The values for o,p-DDT of alpha and R(s) varied from 1.24 to 2.52 and from 0.80 to 2.47, respectively. The values of alpha and R(s) for o,p-DDD were 1.26 and 0.60, respectively.