Chemosensitizing interactions of clofazimine and B669 with human K562 erythroleukaemia cells with varying levels of expression of P-glycoprotein

Clofazimine: A journey of a drug

Among different strategies to develop novel therapies, drug repositioning (aka repurposing) aims at identifying new uses of an already approved or investigational drug. This approach has the advantages of availability of the extensive pre-existing knowledge of the drug's safety, pharmacology and toxicology, manufacturing and formulation. It provides advantages to the risk-versus-rewards trade-off as compared to the costly and time-consuming de novo drug discovery process. Clofazimine, a red-colored synthetic derivative of riminophenazines initially isolated from lichens, was first synthesized in the 1950 s, and passed through several phases of repositioning in its history as a drug. Being initially developed as an anti-tuberculosis treatment, it was repurposed for the treatment of leprosy, prior to re-repositioning for the treatment of multidrug-resistant tuberculosis and other infections. Since 1990 s, reports on the anticancer properties of clofazimine, both in vitro and in vivo, started to appear. Among the diverse mechanisms of action proposed, the activity of clofazimine as a specific inhibitor of the oncogenic Wnt signaling pathway has recently emerged as the promising targeting mechanism of the drug against breast, colon, liver, and other forms of cancer. Seventy years after the initial discovery, clofazimine's journey as a drug finding new applications continues, serving as a colorful illustration of drug repurposing in modern pharmacology.

Mining Natural Compounds to Target WNT Signaling: Land and Sea Tales

WNT signaling plays paramount roles in organism development, physiology, and disease, representing a highly attractive target for drug development. However, no WNT-modulating drugs have been approved, with several candidates trudging through the early clinical trials. This delay instigates alternative approaches to discover WNT-modulating drugs. Natural products were the source of therapeutics for centuries, but the chemical diversity they offer, especially when looking at different taxonomic groups and habitats, is still to a large extent unexplored. These considerations urge researchers to screen natural compounds for the WNT-modulatory activities. Since several reviews on such endeavors exist, we here have attempted to present these efforts as "Land and sea tales" (citing the book title by Rudyard Kipling) superimposing them onto the traditional pipeline of drug discovery and early development. In doing so, we illustrate each step of the pipeline with case studies stemming from our own research. It will become obvious that several steps of the pipeline need to be modified when applied to natural products rather than to synthetic libraries. Yet the main message of this chapter is that natural compounds represent a powerful source for the WNT signaling modulators and can be developed towards drug candidates against WNT-dependent maladies.

Towards the first targeted therapy for triple-negative breast cancer: Repositioning of clofazimine as a chemotherapy-compatible selective Wnt pathway inhibitor

Wnt signaling is overactivated in triple-negative breast cancer (TNBC) and several other cancers, and its suppression emerges as an effective anticancer treatment. However, no drugs targeting the Wnt pathway exist on the market nor in advanced clinical trials. Here we provide a comprehensive body of preclinical evidence that an anti-leprotic drug clofazimine is effective against TNBC. Clofazimine specifically inhibits canonical Wnt signaling in a panel of TNBC cells in vitro. In several mouse xenograft models of TNBC, clofazimine efficiently suppresses tumor growth, correlating with in vivo inhibition of the Wnt pathway in the tumors. Clofazimine is well compatible with doxorubicin, exerting additive effects on tumor growth suppression, producing no adverse effects. Its excellent and well-characterized pharmacokinetics profile, lack of serious adverse effects at moderate (yet therapeutically effective) doses, its combinability with cytotoxic therapeutics, and the novel mechanistic mode of action make clofazimine a prime candidate for the repositioning clinical trials. Our work may bring forward the anti-Wnt targeted therapy, desperately needed for thousands of patients currently lacking targeted treatments.

A new therapeutic combination for osteosarcoma: Gemcitabine and Clofazimine co-loaded liposomal formulation

Osteosarcoma is the most common cancer in bone. Drug resistance is a challenge of current treatments that needs to be improved with novel treatment strategies. In this research, a new dual drug delivery system was developed with Gemcitabine (GEM) and Clofazimine (CLF) co-loaded liposome formulations. GEM is a well-known anticancer agent and CLF is a leprostatic and anti-inflammatory drug recently recognized as effective on cancer. GEM and CLF co-loaded liposomal formulation was achieved with compartmentalization as hydrophilic GEM being in core and lipophilic CLF sequestering in lipid-bilayer. Liposomes had high encapsulation efficiency (above 90%, GEM and above 80%, CLF). CLF release was enhanced while GEM release was slowed down in co-loaded liposomes compared to single cases. GEM/CLF co-loaded liposomes significantly enhanced cytotoxicity than GEM or CLF loaded liposomes on osteosarcoma cell line. CLF and GEM had synergistic effect (CI < 1). Results of flow cytometry showed higher apoptotic cell ratio, caspase-3 activity, mitochondrial membrane depolarized cells' ratio for GEM/CLF co-loaded liposome treatments than other liposomes. Cytotoxicity of CLF on bone cancer cells and also its synergistic effect with GEM on osteosarcoma is reported for the first time with this study. CLF's loading with GEM into liposome was also a new approach for enhancement of anticancer effect on Saos-2 cells. Therefore, GEM/CLF co-loaded liposomal delivery system is proposed as a novel approach for treatment of osteosarcoma.

Anti-cancer effect of clofazimine as a single agent and in combination with cisplatin on U266 multiple myeloma cell line

Multiple Myeloma (MM) is a malignant neoplasm of bone marrow plasma B cells with high morbidity. Clofazimine (CLF) is an FDA-approved leprostatic, anti-tuberculosis, and anti-inflammatory drug that was previously shown to have growth suppression effect on various cancer types such as hepatocellular, lung, cervix, esophageal, colon, and breast cancer as well as melanoma, neuroblastoma, and leukemia. The objective of this study was to evaluate the anticancer effect and mechanism of CLF on U266 MM cell line. CLF (10μM, 24h) treatment resulted up to 72% growth suppression on a panel of hematological cell lines. Dose-response study conducted on U266 MM cell line revealed an IC₅₀ value of 9.8±0.7μM. CLF also showed a synergistic inhibition effect in combination with cisplatin. In mechanistic assays, CLF treatment caused mitochondrial membrane depolarization, change in cell membrane asymmetry and increase in caspase-3 activity; indicating to an intrinsic apoptosis mechanism. This study provides new evidence for the anticancer effect of CLF on U266 cell line. Further in vivo and clinical studies are warranted to evaluate its therapeutic potential for MM treatment.

Anticancer efficacy and toxicokinetics of a novel paclitaxel-clofazimine nanoparticulate co-formulation

Contemporary chemotherapy is limited by disseminated, resistant cancer. Targeting nanoparticulate drug delivery systems that encapsulate synergistic drug combinations are a rational means to increase the therapeutic index of chemotherapeutics. A lipopolymeric micelle co-encapsulating an in vitro optimized, synergistic fixed-ratio combination of paclitaxel (PTX) and clofazimine (B663) has been developed and called Riminocelles™. The present pre-clinical study investigated the acute toxicity, systemic exposure, repeat dose toxicity and efficacy of Riminocelles in parallel to Taxol® at an equivalent PTX dose of 10 mg/kg. Daily and weekly dosing schedules were evaluated against Pgp-expressing human colon adenocarcinoma (HCT-15) xenografts implanted subcutaneously in athymic mice. Riminocelles produced statistically significant (p <  .05) tumor growth delays of 3.2 and 2.7 days for the respective schedules in contrast to Taxol delaying growth by 0.5 and 0.6 days. Using the control tumor doubling time of 4.2 days, tumor-cell-kill values of 0.23 for Riminocelles and 0.04 for Taxol following daily schedules were calculated. A significant weight loss of 5.7% after 14 days (p < 0.05) relative to the control group (n = 8) was observed for the daily Taxol group whereas Riminocelles did not incur significant weight loss neither were blood markers of toxicity elevated after acute administration (n = 3). The safety and efficacy of Riminocelles is statistically superior to Taxol. However, passive tumor targeting was not achieved and the tumor burden progressed quickly. Prior to further animal studies, the in vivo thermodynamic instability of the simple lipopolymeric micellular delivery system requires improvement so as to maintain and selectively deliver the fixed-ratio drug combination.

Comparative study of the effects of antituberculosis drugs and antiretroviral drugs on cytochrome P450 3A4 and P-glycoprotein

Predicting drug-drug interactions (DDIs) related to cytochrome P450 (CYP), such as CYP3A4 and one of the major drug transporters, P-glycoprotein (P-gp), is crucial in the development of future chemotherapeutic regimens to treat tuberculosis (TB) and TB/AIDS coinfection cases. We evaluated the effects of 30 anti-TB drugs, novel candidates, macrolides, and representative antiretroviral drugs on human CYP3A4 activity using a commercially available screening kit for CYP3A4 inhibitors and a human hepatocyte, HepaRG. Moreover, in order to estimate the interactions of these drugs with human P-gp, screening for substrates was performed. For some substrates, P-gp inhibition tests were carried out using P-gp-expressing MDCK cells. As a result, almost all the compounds showed the expected effects on human CYP3A4 both in the in vitro screening and in HepaRG cells. Importantly, the unproven mechanisms of DDIs caused by WHO group 5 drugs, thioamides, and p-aminosalicylic acid were elucidated. Intriguingly, clofazimine (CFZ) exhibited weak inductive effects on CYP3A4 at >0.25 μM in HepaRG cells, while an inhibitory effect was observed at 1.69 μM in the in vitro screening, suggesting that CFZ autoinduces CYP3A4 in the human liver. Our method, based on one of the pharmacokinetics parameters in humans, provides more practical information associated with not only DDIs but also with drug metabolism.

Amelioration of cisplatin toxicity by a fermented grain food product

The most noticeable hypothesis regarding the pathogenesis of cisplatin toxicity, seen mainly in kidney and intestine, is oxidative stress, an imbalance between free-radical generating cisplatin and radical scavenging systems. This paper describes the role of the antioxidant system in cisplatin-induced toxicity and the protective effect by a processed grain food (Antioxidant Biofactor: AOB), which has been shown to exhibit strong antioxidant activity. Male Fischer 344 rats were used. They were pre-fed either a basal diet (control, 15 g/day) or the diet supplemented with AOB to provide 6.5% or 20% of total diet throughout the experiment. Cisplatin (5 mg/kg, i.v.) was administered at the start of the experiment, and the animals were sacrificed 5 days later. Blood urea nitrogen (BUN) and plasma creatinine, NO2(-) and NO3(-) (NOx) were determined from the plasma. The levels of 4-hydroxy-2-nonenal (a lipid peroxidation product), 8-hydroxy-deoxyguanosine (8-OHdG, an oxidatively modified DNA adduct) and nitrotyrosine were histologically analyzed. The cisplatin administration resulted in a loss of body weight and elevations of BUN, serum creatinine and NOx levels, whereas AOB supplement reversed these effects. The severe morphological damages induced in the kidney and intestine by the cisplatin administration were markedly improved in the AOB group. The levels of lipid peroxidation, 8-OHdG, and nitrotyrosine all paralleled the morphological damage. The AOB effect was dose dependent. In conclusion, the present study suggests that certain food additives like AOB may be of benefit against the side effects of cisplatin.