Electromotive drug administration

Studies analyzing the pharmacokinetics of intravesical chemotherapy delivery noted that treatment of bladder cancer cells located deep to the superficial cell layer was inadequate. This was thought to be secondary to decreased drug concentrations beyond the urothelium, and electromotive therapy was proposed as a means to improve drug penetration. When exposed to a conductive current such as NaCl and an electrical field, mitomycin (MMC) delivery across the urothelium increases as a result of current-induced convective flow of water. Thus, water will bring the nonionized MMC particle with it across the urothelium as it travels down its electrical gradient. Results indicated that mean concentration of MMC in the bladder wall delivered by electromotive drug administration vastly exceeded MMC concentration achieved through passive delivery by a factor of almost 7.

In a randomized controlled trial of adjuvant treatment following complete transurethral resection, patients with T1 bladder cancer assigned sequential BCG and electromotive MMC had a longer disease-free interval than did those assigned BCG alone. However, because patients in the control group did not receive standard maintenance BCG therapy, the benefit of this therapy over standard BCG remains to be tested. More recently, benefit of electromotive therapy was also observed in the perioperative setting. In a phase 3 study enrolling patients with NMIBC, the efficacy of TURBT alone was compared with that of immediate post-TURBT passive diffusion MMC or immediate pre-TURBT electromotive MMC. With a median follow-up of over 7 years, disease-free rates were: 36%, 41%, and 62% of patients treated with TURBT alone, post-TURBT passive diffusion of MMC, and pre-TURBT electromotive administration of MMC, respectively. This represents a 21% absolute improvement in disease-free rate over passive diffusion. Electromotive MMC is not currently approved by the FDA.

Nanoparticle-based therapy

Small molecule platform nanoparticles can be engineered to increase the drug contact time with the urothelium by functioning as controlled drug release systems. They are specifically created to have multiple functional groups (eg, albumin, amine, carboxyl, or sulfhydryl) that can interact with the urothelium in order to increase adhesion rates. Nanoparticle albumin-bound (NAB) agents are currently under clinical investigation. The addition of albumin is proposed to increase solubility and facilitate drug delivery to tumor cells through biological interactions with albumin receptors that facilitate drug transport across epithelial cells. Intravesical administration of NAB linked with paclitaxel demonstrated safety and tolerability in a phase 1 trial including 18 patients with BCG-refractory high-grade Ta, T1, or carcinoma-in-situ (CIS). Results of the phase 2 data were recently reported. A complete response was observed in 10 (35.7%) of 28 patients treated with NAB-paclitaxel with recurrent NMIBC who had failed at least 1 prior BCG regimen.

In murine models, the mTOR inhibitor rapamycin was found to potentiate the induction of BCG-mediated immune responses in mice. In addition, rapamycin demonstrated antitumor activity in preclinical models of bladder cancer. Albumin-bound rapamycin (ABI-009) could facilitate uptake of rapamycin, which is normally water-insoluble. This novel agent is currently being tested in early clinical trials for patients with BCG-refractory or recurrent NMIBC ( NCT02009332 ).

Hydrogel formulations

One potential means to improve contact duration of intravesical therapy, including BCG, is through the use of a hydrogel delivery system. Thermosensitive hydrogels are able to exist as a free-flowing solution at room temperature, while becoming a viscous hydrogel at body temperature. BCG introduced with this gel system could prove to be a valuable intravesical immunotherapeutic agent because of its ability to lead to sustained release of BCG as compared to the typical 2 hour duration witnessed in current BCG intravesical therapy delivery. TC-3 is a hydrogel application currently under clinical investigation that uses a biodegradable gel, which remains in gel form to function as a drug reservoir inside the bladder, and dissolves when it comes in contact with the urine. A randomized trial of pre-TURBT administration is proposed to evaluate effects of MMC mixed with TC-3 gel on patients with papillary low risk recurrent NMIBC ( NCT01803295 ).

Hyperthermia

Hyperthermia has been shown to increase urothelium penetration rate of immuno- and chemo-therapeutic agents and has the potential to be an effective delivery method. Prospective cohort data from patients with NMIBC who had received prior intravesical therapy chemohyperthermia given by means of Synergo suggested that chemohyperthermia had potential to provide effective approach. Patients underwent local microwave induced hyperthermia with a 915 MHz intravesical microwave applicator in addition to either MMC or epirubicin. While lacking a control group, an impressive 2-year disease-free interval of 47% and limited progression to muscle invasive disease (only 4%) among patients who had failed prior therapy was observed. Subsequently, intravesical thermochemotherapy by means of Synergo versus chemotherapy alone with MMC was tested in a randomized trial of 83 patients. Results demonstrated a 10-year disease free survival rate in the thermochemotherapy arm. Further comparative trials are warranted, however, as less favorable results with significant adverse events have been described. In a report of 21 patients treated with thermochemotherapy using Synergo, therapy was abandoned because of adverse effects in 38% of patients and there was limited tumor response.

Another heating device, the BSD-2000, was tested in a pilot study of patients with BCG refractory NMIBC. Fifteen patients were treated with external deep pelvic hyperthermia combined with MMC. The bladders were heated to 42°C for 1 hour during intravesical MMC treatment. Full treatment course was attained in 73% of subjects and the device was deemed safe. Of note, heat-induced swelling of the abdominal skin was reported in 27% of patients.

Hyaluronidase

Increased extracellular matrix deposition is a finding observed in various solid tumors. Increased levels of hyaluronan lead to decreased elasticity of tumor tissue. By hydrolyzing hyaluronan, hyaluronidase can increase permeability of chemotherapy into solid tumors. A phase I safety and tolerability study of immediate post-operative intravesical instillation of Chemophase is described for patients with any stage NMIBC ( NCT00782587 ). In this study, patients will be administered a single immediate post-operative intravesical instillation of recombinant human hyaluronidase in combination with mitomycin.

Adenovirus CD40L

Adenovirus CD40L (AdCD40L) immunogene therapy for bladder cancer has undergone clinical testing. CD40 is a costimulatory protein found on antigen presenting cells such as dendritic cells. Binding of CD40 to CD40L, expressed on Th cells, activates the antigen-presenting cell. The proposed mechanism of action for this therapy is that increased expression of CD40L following adenoviral-mediated delivery disrupts tumor escape mechanisms, thereby allowing for improved tumor eradication in preclinical models. In a clinical trial, 8 patients with Ta bladder cancer were treated with 3 cycles of weekly adCD40L therapy. The therapy was well tolerated, and gene transfer was detected through biopsied tissue.

Recombinant adenovirus

The retinoblastoma tumor suppressor protein (RB) pathway is often deregulated in bladder cancer. Recombinant adenovirus (CG0070) was developed to specifically target this pathway and facilitate precise antitumor activity. CG0070 is a replication selective serotype-5 oncolytic adenovirus that is able to lead to cancer-targeted replication and granulocyte macrophage-colony stimulating factor (GM-CSF) transgene expression. This is accomplished through the E2F-1 promoter element, which in turn is regulated by RB, which aids in controlling viral replication rate as well as the expression of GM-CSF. GM-CSF is directly responsible for stimulating maturation and recruitment of myeloid cells as well as functions as a direct inducer of local antitumor immunity. The targeted antitumor activity of CG0070 is finally achieved through preferential replication within RB-defective bladder cancer cells. A phase 1/2 clinical trial treating 35 patients with either single or multiple intravesical treatments and testing several different doses of CG0070 was conducted. Results showed that urinary CG0070 genome levels were found to be markedly elevated above baseline in approximately 90% of the patients. The drug was well tolerated with minimal adverse effects reported. Although not designed to evaluate efficacy, a complete response rate of 48.6% was noted at 10.4 months. An efficacy study for patients with high-grade non-muscle invasive bladder cancer who have received at least 2 prior courses of intravesical therapy is underway ( NCT01438112 ).

Instiladrin

Although interferon-α2b is known to be an important mediator of antitumor immunity, it has not been adequately tested to determine its value as monotherapy for NMIBC. One potential explanation for its limited antitumor capacity is the limited urothelium exposure duration. A recombinant adenovirus-mediated interferon-α2b protein (rAD-IFN-α) attached to SCH 209702 (Syn3) was developed for intravesical therapy of bladder cancer. Syn3 is a novel excipient that markedly improves the rate at which adenoviral-mediated transduction of urothelium and NMIBC occurs. In a phase 1 trial involving 17 patients, adverse effects were minimal, and the drug was well tolerated; 43% (6 of 13) of patients treated with detectable urine IFN-α levels achieved a complete response at 3 months, with average duration of response lasting 31 months. Of note, 2 patients were disease-free at 29 and 39.2 months. On the other hand, 0% (0 of 1) of patients treated at the same dose, without detectable urine IFN-α levels, achieved complete response. These promising results have led to a phase 2 study for patients with high-grade BCG-refractory or relapsed NMIBC where relapse is defined as recurrence within 1 year after a complete response to BCG treatment ( NCT01687244 ).

BC-819

BC-819 (DTA-H19) is a double-stranded DNA plasmid carrying the gene for the A subunit of diphtheria toxin under the regulation of the H19 gene promoter. H19 is an oncofetal gene encoding for an RNA that acts as a riboregulator and is expressed at high levels in various malignant tissues. A marker lesion study of intravesical BC-819 demonstrated safety and complete ablation of a marker tumor without any new tumor formation in 4 of 18 patients (22% complete response rate). A follow-up study to include 47 patients with intermediate-risk, recurrent, multiple nonmuscle invasive tumors observed complete tumor ablation in 33% of patients and prevented the growth of new tumors in 64% of patients.

Apaziquone

Apaziquone, (EO9), is a synthetic indoloquinone-based bioreductive alkylating agent that becomes cytotoxic following activation by the enzyme deoxythymidine–diaphorase. Deoxythymidine–diaphorase is preferentially expressed at higher concentrations within bladder cancer cells, leading to the potential for targeted anticancer therapy. Because of this, apaziquone was demonstrated as needing 6 to 78 times less concentration than that of MMC to achieve 50% cell death, depending upon the bladder cancer cell line utilized. A marker lesion study demonstrated a complete response in 67.4% of 46 patients with Ta-T1 G1-2 bladder cancer. In a phase 2 study of intermediate- and high-risk patients, recurrent tumors were seen in only 34.7% of patients at 1 year, and only 1 patient had progressed to muscle-invasive disease. These results prompted phase 3 trials of single-dose intravesical apaziquone (EOquin) in the early postoperative period for patients undergoing transurethral resection of NMIBC ( NCT00598806 ) and multiple instillations as adjuvant therapy ( NCT01410565 ).

Pirarubicin

Pirarubicin, an anthracycline analogue of doxorubicin, functions via 2 different mechanisms. It directly inhibits DNA replication and repair through DNA intercalation, and it interacts with topoisomerase II, thereby preventing adequate RNA and protein synthesis. A clinical study of single post-TURBT instillation of pirarubicin in patients with Ta-T1 bladder cancer demonstrated nonrecurrence rates of 92.4%, 82.7%, and 78.8% at 1, 2, and 3-year follow-up, respectively. In addition, a randomized study of Ta-T1 bladder cancer subjected to post-TURBT pirarubicin and weekly treatment for 8 weeks versus 8 weekly treatments demonstrated recurrence rates of 7.8% and 14.3% at 18-month follow-up, respectively.

Oportuzumab monatox

Epithelial cell adhesion molecule (EpCAM) overexpression has been associated with higher grade of bladder cancer. Oportuzumab monatox (OM) is a recombinant fusion protein of humanized anti-EpCAM antibody linked to Pseudomonas exotoxin A. Once OM is bound to the bladder cancer cell in question and internalized, the exotoxin induces apoptosis. A phase 2 trial involving 45 total patients evaluated 2 OM dosing strategies, specifically focusing on BCG-refractory carcinoma in situ. Both treatment schedules were based upon a prior study using OM, with an initial induction cycle followed by 3 weekly instillations at 3-month intervals. OM demonstrated complete response rates of 26.7% and 15.6% at the 6- and 12-month intervals, respectively.

Tamoxifen

Tamoxifen belongs to the class of medications known as selective estrogen receptor modulators, which function as agonists of estrogen receptors in certain tissues (endometrium) and antagonists in others (breast). Although it is widely known that bladder cancer has a much higher prevalence in men, several studies have theorized this is because of increased estrogen levels in women. For example, late menopause and use of oral contraceptives and hormone replacement therapy are associated with lower risk of bladder cancer. Estrogen receptors (ERs) have been demonstrated to be expressed in normal urothelium as well as bladder cancer, with ERβ detected in up to 81% of bladder cancers; increased levels of expression are associated with higher-grade tumors. Preclinical evidence for antiproliferation of bladder tumors with tamoxifen has been observed. Female mice were given a known bladder-specific carcinogen, N-butyl-N-(4-hydroxylbutyl) nitrosamine (BBN), which resulted in 76% tumor incidence in the control group and only 10% to 14% incidence in the tamoxifen-treated group. Tamoxifen is currently being evaluated in a phase 2 study of low- to intermediate-risk NMIBC, with a focus on pharmacodynamic effects ( NCT02197897 ).

Checkpoint inhibitors

Novel checkpoint inhibitors, including PD-1 and PD-L1 inhibitors, have demonstrated impressive and durable antitumor response in advanced, metastatic bladder cancer, and this has prompted considerations for testing in NMIBC. Currently there is one trial utilizing a checkpoint inhibitor in combination with BCG listed in clinicaltrials.gov , but others are expected. The PD-1 inhibitor, pembrolizumab (also known as MK-3475), is being tested in a phase 1 study in combination with BCG for patients with high-risk NMIBC ( NCT02324582 ).

Lenalidomide

Lenalidomide, an analogue of thalidomide, has several known mechanisms of action and is currently FDA approved for the treatment of specific types of myelodysplastic syndrome and multiple myeloma. It inhibits angiogenesis, induces tumor cell apoptosis, and has an immunomodulatory role. In a preclinical trial, lenalidomide, in combination with BCG, was evaluated for its efficacy in MBT-2 cell lines implanted in immunocompetent mice, with results demonstrating a statistically significant decrease in tumor size. Lenalidomide is being tested in combination with BCG in a phase 2 trial of high-risk NMIBC ( NCT01373294 ).

Toll-like receptor agonist

Toll-like receptors (TLRs) are pattern-recognition receptors, which, when activated, alert the immune system to presence of microbes and are primary signaling mechanisms for the innate immune response. TLR agonists are a promising target for bladder cancer therapy, as BCG is a known TLR agonist. Imiquimod is a TLR-7 agonist and is FDA approved for the treatment of superficial basal cell carcinoma. TLR-7 agonists have been tested in preclinical models of bladder cancer, with some evidence of antitumor activity. In the clinical setting, TMX-101, a variant formulation of imiquimod, was tested in a phase 1 trial demonstrating safety in 16 patients. A phase 2 trial ( NCT01731652 ) has been developed.