Enhancing PDT efficacy in NMIBC: Efflux inhibitor mediated improvement of PpIX levels and efficacy of the combination of PpIX-PDT and SO-cleavable prodrugs.

Protoporphyrin IX (PpIX)-based photodynamic therapy (PDT) has shown limited efficacy in nonmuscle-invasive bladder cancer (NMIBC). To improve PDT efficacy, we developed singlet oxygen-cleavable prodrugs. These prodrugs, when combined with PpIX-PDT, induce cancer cell death through both PDT and drug release mechanisms. Inhibition of PpIX efflux was reported to be an effective strategy to improve PpIX-PDT in certain cancer cells. Our main goal was to investigate whether adding an efflux inhibitor to the combination of PpIX and prodrugs can improve the PpIX levels in bladder cancer cells and the release of active drugs, thus improving the overall efficacy of the treatment. We treated bladder cancer cell lines with lapatinib and evaluated intracellular PpIX fluorescence, finding significantly increased accumulation. Combining lapatinib with prodrugs led to significantly reduced cell viability compared to prodrugs or PpIX-PDT alone. The effect of lapatinib depended on the expression level of the efflux pump in bladder cancer cells. Interestingly, lapatinib increased paclitaxel (PTX) prodrug uptake by threefold compared to prodrug alone. Adding an efflux inhibitor (e.g., lapatinib) into bladder instillation solutions could be a straightforward and effective strategy for NMIBC treatment, particularly in tumors expressing efflux pumps, with the potential for clinical translation.

Mitochondrial targeting improves the selectivity of singlet-oxygen cleavable prodrugs in NMIBC treatment.

Mitochondria play an essential role in cancer treatment by providing apoptotic signals. Hexyl aminolevulinate, an FDA-approved diagnosis for non-muscle invasive bladder cancer, induces the production of protoporphyrin IX (PpIX) preferentially by mitochondria in cancer cells. Photosensitizer PpIX upon illumination can release active chemotherapy drugs from singlet oxygen-activatable prodrugs. Prodrugs placed close enough to PpIX formed in mitochondria can improve the antitumor efficiency of PpIX-PDT. The preferred uptake of prodrugs by cancer cells and tumors can further enhance the selective damage of cancer cells over non-cancer cells and surrounding normal tissues. Mitochondriotropic prodrugs of anticancer drugs, such as paclitaxel and SN-38, were synthesized using rhodamine, a mitochondrial-targeting moiety. In vitro, the mitochondrial targeting helped achieve preferential cellular uptake in cancer cells. In RT112 cells (human bladder cancer cells), intracellular prodrug concentrations were 2-3 times higher than the intracellular prodrug concentrations in BdEC cells (human bladder epithelial cells), after 2 h incubation. In an orthotopic rat bladder tumor model, mitochondria-targeted prodrugs achieved as much as 34 times higher prodrug diffusion in the tumor area compared to the nontumor bladder area. Overall, mitochondria targeting made prodrugs more effective in targeting cancer cells and tumors over non-tumor areas, thereby reducing nonspecific toxicity.

Comparison of red and green light for treating non-muscle invasive bladder cancer in rats using singlet oxygen-cleavable prodrugs with PPIX-PDT.

It has been 30 years since Photofrin-PDT was approved for the treatment of bladder cancer in Canada. However, Photofrin-PDT failed to gain popularity due to bladder complications. The PDT with red light and IV-administered Photofrin could permanently damage the bladder muscle. We have been developing a new combination strategy of PpIX-PDT with singlet oxygen-cleavable prodrugs for NMIBC with minimal side effects, avoiding damage to the bladder muscle layer. PpIX can be excited by either green (532 nm) or red (635 nm) light. Red light could be more efficacious in vivo due to its deeper tissue penetration than green light. Since HAL preferentially produces PpIX in tumors, we hypothesized that illuminating PpIX with red light might spare the muscle layer. PpIX-PDT was used to compare green and red laser efficacy in vitro and in vivo. The IC50 of in vitro PpIX-PDT was 18 mW/cm2 with the red laser and 22 mW/cm2 with the green laser. The in vivo efficacy of the red laser with 50, 75, and 100 mW total dose was similar to the same dose of green laser in reducing tumor volume. Combining PpIX-PDT with prodrugs methyl-linked mitomycin C (Mt-L-MMC) and rhodamine-linked SN-38 (Rh-L-SN-38) significantly improved efficacy (tumor volume comparison). PpIX-PDT or PpIX-PDT + prodrug combination did not cause muscle damage in histological analysis. Overall, a combination of PpIX-PDT and prodrug with 635 nm laser is promising for non-muscle invasive bladder cancer treatment.

Preclinical evaluation of singlet oxygen-cleavable prodrugs in combination with protoporphyrin IX-photodynamic therapy in an orthotopic rat model of non-muscle-invasive bladder cancer†.

Photodynamic therapy (PDT) initially employed red light, which caused some patients to experience permanent bladder contractions. PDT using the FDA-approved drug hexaminolevulinate (HAL), which produces protoporphyrin IX (PpIX) in the tumor, showed some promise but has low efficacy in treating non-muscle-invasive bladder cancer (NMIBC). We developed singlet oxygen-activatable prodrugs of two anticancer drugs, paclitaxel and mitomycin C, to enhance the antitumor effect of PpIX-PDT without producing systemic side effects, by promoting only local release of the active chemotherapeutic agent. Orthotopic NMIBC model was used to compare the efficacy of prodrugs only, PpIX-PDT, and prodrugs + PpIX-PDT. 532 nm laser with a total power of 50 mW for 20 min (60 J, single treatment) was used with HAL and prodrugs. Histology and microscopic methods with image analysis were used to evaluate the tumor staging, antitumor efficacy, and local toxicity. Prodrug + PpIX-PDT produced superior antitumor efficacy than PpIX-PDT alone with statistical significance. Both PpIX-PDT alone and combination therapy resulted in mild damage to the bladder epithelium in the normal bladder area with no apparent damage to the muscle layer. Overall, SO-cleavable prodrugs improved the antitumor efficacy of PpIX-PDT without causing severe and permanent damage to the bladder muscle layer.

Photodynamic Therapy for Bladder Cancers, A Focused Review†.

Bladder cancer is the first cancer for which PDT was clinically approved in 1993. Unfortunately, it was unsuccessful due to side effects like bladder contraction. Here, we summarized the recent progress of PDT for bladder cancers, focusing on photosensitizers and formulations. General strategies to minimize side effects are intravesical administration of photosensitizers, use of targeting strategies for photosensitizers and better control of light. Non-muscle invasive bladder cancers are more suitable for PDT than muscle invasive and metastatic bladder cancers. In 2010, the FDA approved blue light cystoscopy, using PpIX fluorescence, for photodynamic diagnosis of non-muscle invasive bladder cancer. PpIX produced from HAL was also used in PDT but was not successful due to low therapeutic efficacy. To enhance the efficacy of PpIX-PDT, we have been working on combining it with singlet oxygen-activatable prodrugs. The use of these prodrugs increases the therapeutic efficacy of the PpIX-PDT. It also improves tumor selectivity of the prodrugs due to the preferential formation of PpIX in cancer cells resulting in decreased off-target toxicity. Future challenges include improving prodrugs and light delivery across the bladder barrier to deeper tumor tissue and generating an effective therapeutic response in an In vivo setting without causing collateral damage to bladder function.

Singlet Oxygen Activatable Prodrugs of Paclitaxel, SN-38, MMC and CA4: Nonmitochondria-Targeted Prodrugs.

We established a light-activatable prodrug strategy that produces the combination effect of photodynamic therapy (PDT) and site-specific chemotherapy. Prodrugs are activated by singlet oxygen (SO), generated from PS and visible or near IR light, in either intra- or inter-molecular manner. The goal of this study is to evaluate cytotoxic effects of nonmitochondria-targeted prodrugs of a number of anticancer drugs with different mechanisms of action. They were tested in both 2D and 3D in vitro conditions via inter-molecular activation of prodrugs by SO generated in mitochondria by protoporphyrin IX-PDT (PpIX-PDT). Prodrugs of anticancer drugs (paclitaxel, SN-38, combretastatin A4 and mitomycin C) were synthesized using facile and high-yielding reactions. Nonmitochondria-targeted prodrugs showed limited dark toxicity while all of them showed greatly enhanced phototoxicity compared to PpIX-PDT in the 2D culture model. Prodrugs generated up to about 95% cell killing at 2.5 µM when administered with hexyl-aminolevulinate (HAL) to produce Protoporphyrin IX in cancer cells in both 2D monolayer and 3D spheroids model. The data demonstrate that mitochondria-targeting of prodrugs is not fully essential for our inter-molecular activation prodrug strategy. The prodrug strategy also worked for anticancer drugs with diverse MOAs.

Singlet oxygen-activatable Paclitaxel prodrugs via intermolecular activation for combined PDT and chemotherapy.

Systemic side effects and high hydrophobicity are major disadvantages of paclitaxel (PTX), one of the most popular anticancer drugs. Here, we present singlet oxygen (SO)-activatable and mitochondria-targeted PTX prodrugs to overcome these problems and boost the cytotoxic effect of photodynamic therapy (PDT). Three PTX prodrugs were prepared by conjugating PTX with various cationic groups. Hydrophobicity was determined in LogD7.4 value. Mitochondrial localization was confirmed by fluorescence confocal microscopy and uptake of mitochondria-specific fluorescence probe. Dark- and photo-toxicity were measured in AY-27 cells with MTT assay. All three prodrugs showed better hydrophilicity than PTX and improved phototoxicity when combined with protoporphyrin IX (PpIX) PDT. In conclusion, SO-activatable and higher hydrophilic PTX prodrugs were successfully prepared. This approach could be used to improve the antitumor efficacy of PDT without the systemic side effects of PTX.

Analgesic principle from Curcuma amada.

ETHNOPHARMACOLOGICAL RELEVANCE: The rhizome of Curcuma amada has been used as a folk medicine for the treatment of rheumatic disorders in the northern part of Bangladesh and has also used for the treatment of inflammation and fever in the Ayurvedic and Unani systems of medicine. Aim of the study was to investigate the analgesic principle of the MeOH extract of the rhizome of Curcuma amada by an in vivo bioassay guided chromatographic separation and purification, and the structure elucidation of the purified compound by spectroscopic methods. MATERIALS AND METHODS: Dried powder of Curcuma amada rhizomes was extracted with MeOH. The analgesic activity of the crude extract and its chromatographic fractions as well as the purified compound itself was evaluated by the acetic acid induced writhing method and the formalin induced licking test in Swiss albino mice. The MeOH extract was separated by chromatographic methods and the pure active compound was purified by crystallization in hexanes. The structure of the pure compound was then elucidated by spectroscopic methods. RESULTS: The MeOH extract of Curcuma amada exhibited 41.63% and 45.53% inhibitions in the acetic acid induced writhing method at doses of 200mg/kg and 400mg/kg, respectively. It also exerted 20.43% and 28.50% inhibitions in early phase at doses of 200mg/kg and 400mg/kg, respectively, and 30.41% and 42.95% inhibitions in late phase at doses of 200mg/kg and 400mg/kg, respectively in the formalin induced licking test. Vacuum Liquid Chromatography (VLC) of crude extract yielded five fractions and Fr. 1 was found to have the most potent analgesic activity with inhibitions of 36.96% in the acetic acid induced writhing method and 47.51% (early phase), 39.50% (late phase) in the formalin induced licking test at a dose of 200mg/kg. Column chromatography of Fr. 1 on silica gel generated seven fractions (SF. 1-SF. 7). SF. 2 showed the most potent activity with inhibition of 49.81% in the acetic acid induced writhing method at a dose of 100mg/kg. Crystallization of SF. 2 yielded (1) (zederone, 520mg). It showed statistically significant inhibitions of 38.91% and 52.14% in the acetic acid induced writhing method at doses of 20mg/kg and 40mg/kg, respectively. Moreover, it also showed statistically significant inhibitions of 27.79% and 29.93% (early phase) and of 38.24% and 46.08% (late phase) in the formalin induced licking test at doses of 20mg/kg and 40mg/kg, respectively. CONCLUSION: Isolation and characterization of zederone (1) as analgesic principle of Curcuma amada corroborate its use in Ayurvedic, Unani and folk medicines for the treatment of rheumatic disorders and also contributing to its pharmacological validation.