Cisplatin rescue therapy: experience with sodium thiosulfate, WR2721, and diethyldithiocarbamate

Safety Evaluations of Rapamycin Perfluorocarbon Nanoparticles in Ovarian Tumor-Bearing Mice

Nanomedicine holds great potential for revolutionizing medical treatment. Ongoing research and advancements in nanotechnology are continuously expanding the possibilities, promising significant advancements in healthcare. To fully harness the potential of nanotechnology in medical applications, it is crucial to conduct safety evaluations for the nanomedicines that offer effective benefits in the preclinical stage. Our recent efficacy studies indicated that rapamycin perfluorocarbon (PFC) nanoparticles showed promise in mitigating cisplatin-induced acute kidney injury (AKI). As cisplatin is routinely administered to ovarian cancer patients as their first-line chemotherapy, in this study, we focused on evaluating the safety of rapamycin PFC nanoparticles in mice bearing ovarian tumor xenografts. Specifically, this study evaluated the effects of repeat-dose rapamycin PFC nanoparticle treatment on vital organs, the immune system, and tumor growth and assessed pharmacokinetics and biodistribution. Our results indicated that rapamycin PFC nanoparticle treatment did not cause any detectable adverse effects on cardiac, renal, or hepatic functions or on splenocyte populations, but it reduced the splenocyte secretion of IL-10, TNFα, and IL12p70 upon IgM stimulation. The pharmacokinetics and biodistribution results revealed a significant enhancement in the delivery of rapamycin to tumors by rapamycin PFC nanoparticles, which, in turn, led to a significant reduction in ovarian tumor growth. Therefore, rapamycin PFC nanoparticles have the potential to be clinically beneficial in cisplatin-treated ovarian cancer patients.

An integrated view of cisplatin-induced nephrotoxicity, hepatotoxicity, and cardiotoxicity: characteristics, common molecular mechanisms, and current clinical management

Cisplatin (CP) is a chemotherapy drug widely prescribed to treat various neoplasms. Although fundamental for the therapeutic action of the drug, its cytotoxic mechanisms trigger adverse effects in several tissues, such as the kidney, liver, and heart, which limit its clinical use. In this sense, studies point to an essential role of damage to nuclear and mitochondrial DNA associated with oxidative stress, inflammation, and apoptosis in the pathophysiology of tissue injuries. Due to the limitation of effective preventive and therapeutic measures against CP-induced toxicity, new strategies with potential cytoprotective effects have been studied. Therefore, this article is timely in reviewing the characteristics and main molecular mechanisms common to renal, hepatic, and cardiac toxicity previously described, in addition to addressing the main validated strategies for the current management of these adverse events in clinical practice. We also handle the main promising antioxidant substances recently presented in the literature to encourage the development of new research that consolidates their potential preventive and therapeutic effects against CP-induced cytotoxicity.

Developing a hyperthermic intraperitoneal chemotherapy (HIPEC) gynecologic oncology program: a Canadian experience

Hyperthermic intraperitoneal chemotherapy (HIPEC) is a treatment option for epithelial ovarian cancer following cytoreductive surgery. The intraperitoneal spread of the disease makes the peritoneal cavity an ideal target for drug delivery. HIPEC has shown promising results in improving overall survival in epithelial ovarian cancer patients when performed during interval cytoreductive surgery. Recent studies have provided level 1 evidence supporting increased overall survival in stage III ovarian cancer patients treated with HIPEC during interval cytoreduction. Meta-analyses have further confirmed the survival improvement in women receiving HIPEC. Despite its inclusion in guidelines, many centers have been hesitant to implement HIPEC programs due to perceived obstacles, such as increased morbidity, cost, and resource requirements. Studies have shown that morbidity rates are acceptable in selected patients, and the addition of HIPEC to cytoreductive surgery is cost effective. Therefore, the main barrier to implementing HIPEC programs is related to resource requirements and logistics, but with proper preparation, these challenges can be overcome. Establishing a successful HIPEC program requires institutional support, a knowledgeable and dedicated team, adequate resources and equipment, and proper training and audit. This review aims to provide evidence based information to guide the development of successful HIPEC programs, including preoperative, anesthetic, and surgical considerations. It also reviews the different equipment and protocols for the perfusion and common postoperative events.

The repositioned drugs disulfiram/diethyldithiocarbamate combined to benznidazole: Searching for Chagas disease selective therapy, preventing toxicity and drug resistance

Chagas disease (CD) affects at least 6 million people in 21 South American countries besides several thousand in other nations all over the world. It is estimated that at least 14,000 people die every year of CD. Since vaccines are not available, chemotherapy remains of pivotal relevance. About 30% of the treated patients cannot complete the therapy because of severe adverse reactions. Thus, the search for novel drugs is required. Here we tested the benznidazole (BZ) combination with the repositioned drug disulfiram (DSF) and its derivative diethyldithiocarbamate (DETC) upon Trypanosoma cruzi in vitro and in vivo. DETC-BZ combination was synergistic diminishing epimastigote proliferation and enhancing selective indexes up to over 10-fold. DETC was effective upon amastigotes of the BZ- partially resistant Y and the BZ-resistant Colombiana strains. The combination reduced proliferation even using low concentrations (e.g., 2.5 µM). Scanning electron microscopy revealed membrane discontinuities and cell body volume reduction. Transmission electron microscopy revealed remarkable enlargement of endoplasmic reticulum cisternae besides, dilated mitochondria with decreased electron density and disorganized kinetoplast DNA. At advanced stages, the cytoplasm vacuolation apparently impaired compartmentation. The fluorescent probe H2-DCFDA indicates the increased production of reactive oxygen species associated with enhanced lipid peroxidation in parasites incubated with DETC. The biochemical measurement indicates the downmodulation of thiol expression. DETC inhibited superoxide dismutase activity on parasites was more pronounced than in infected mice. In order to approach the DETC effects on intracellular infection, peritoneal macrophages were infected with Colombiana trypomastigotes. DETC addition diminished parasite numbers and the DETC-BZ combination was effective, despite the low concentrations used. In the murine infection, the combination significantly enhanced animal survival, decreasing parasitemia over BZ. Histopathology revealed that low doses of BZ-treated animals presented myocardial amastigote, not observed in combination-treated animals. The picrosirius collagen staining showed reduced myocardial fibrosis. Aminotransferase de aspartate, Aminotransferase de alanine, Creatine kinase, and urea plasma levels demonstrated that the combination was non-toxic. As DSF and DETC can reduce the toxicity of other drugs and resistance phenotypes, such a combination may be safe and effective.

A chemical perspective on the clinical use of platinum-based anticancer drugs

Platinum drugs have been a mainstay of cancer chemotherapy since the introduction of cisplatin in the 1970s. Since then, carboplatin and oxaliplatin have been approved world-wide and nedaplatin, lobaplatin, heptaplatin, dicycloplatin, and miriplatin have been approved in individual countries. The three main platinum drugs are not used in isolation but are combined in chemotherapy protocols from a range of 28 drugs that include: anthracyclines, alkylating agents, vinca alkaloids, antimetabolites, topoisomerase inhibitors, taxanes, and monoclonal antibodies. Interestingly, they are not yet used in combination with tyrosine kinase inhibitors or proteasome inhibitors. How platinum drugs are formulated for administration to patients is important to minimise aquation during storage and administration. Cisplatin is typically formulated in saline-based solutions while carboplatin and oxaliplatin are formulated in dextrose. Pharmacokinetics are an important factor in both the efficacy and safety of platinum drugs. This includes the quantity of protein-bound drug in blood serum, how fast the drugs are cleared by the body, and how fast the drugs are degraded and deactivated. Attempts to control platinum pharmacokinetics and side effects using rescue agents, macrocycles, and nanoparticles, and through the design of platinum(IV)-based drugs have not yet resulted in clinically successful outcomes. As cancer is predominantly a disease of old age, many cancer patients who are administered a platinum drug may have other medical conditions which means they may also be taking many non-cancer medicines. The co-administration of non-cancer medicines to patients can potentially affect the efficacy of platinum drugs and/or change the severity of their side effects through drug-drug interactions.

Sodium thiosulfate during cisplatin-based hyperthermic intraperitoneal chemotherapy is associated with transient hypernatraemia without clinical sequelae

Objectives

Cisplatin is commonly used during intraperitoneal chemotherapy however has well-established nephrotoxic side-effects. Sodium thiosulfate is often added to cisplatin-based hyperthermic intraperitoneal chemotherapy (HIPEC) protocols to mitigate this, however evidence regarding risk of hypernatraemia is scarce as of yet.

Methods

We retrospectively identified patients undergoing cytoreductive surgery (CRS) for peritoneal surface malignancies of any origin at a single high-volume unit between April 2018 and December 2020. Patients were included if they received cisplatin-based HIPEC with intravenous sodium thiosulfate. Blood tests were collected pre-surgery and then daily during admission. Hypernatraemia was defined as serum sodium >145 mmol/L. Renal impairment was defined using the RIFLE criteria.

Results

Eleven CRSs met inclusion criteria, the majority of which were indicated for ovarian cancer (72.7%). One (9.1%) patient with mesothelioma received mitomycin C as an additional chemotherapy agent. The incidence of hypernatraemia was 100% but all cases were transient, with no clinical sequelae observed. The rate of AKI was 36.4%, with three (27.3%) patients classified as risk and one (9.1%) instance of failure. No long-term renal impairment was observed.

Conclusions

Despite biochemical evidence of mild hypernatraemia but with the absence of clinical sequelae, sodium thiosulfate appears to be safe when used in adjunct to cisplatin-based HIPEC during CRS. These findings should be evaluated with further comparative studies. When describing renal impairment, it is important that standardisation in reporting occurs, with the RIFLE and Acute Kidney Injury Network criteria now the preferred consensus definitions.

Association of Sodium Thiosulfate With Risk of Ototoxic Effects From Platinum-Based Chemotherapy: A Systematic Review and Meta-analysis

IMPORTANCE

Platinum-induced ototoxic effects are a significant issue because platinum-based chemotherapy is one of the most commonly used therapeutic medications. Sodium thiosulfate (STS) is considered a potential otoprotectant for the prevention of platinum-induced ototoxic effects that functions by binding the platinum-based agent, but its administration raises concerns regarding the substantial attenuation of the antineoplastic outcome associated with platinum.

OBJECTIVE

To evaluate the association between concurrent STS and reduced risk of ototoxic effects among patients undergoing platinum-based chemotherapy and to evaluate outcomes, including event-free survival, overall survival, and adverse outcomes.

DATA SOURCES

From inception through November 7, 2020, databases, including the Cochrane Library, PubMed, Embase, Web of Science, and Scopus, were searched.

STUDY SELECTION

Studies enrolling patients with cancer who were undergoing platinum-based chemotherapy that compared ototoxic effects development between patients who received STS and patients who did not and provided adequate information for meta-analysis were regarded as eligible. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines.

DATA EXTRACTION AND SYNTHESIS

The data were extracted by 2 reviewers independently. A random-effects model was used to explore objectives.

MAIN OUTCOMES AND MEASURES

Relative risks (RRs) for ototoxic effects development and hemopoietic event development comparing the experimental group and the control group were estimated. Secondary outcomes were hazard ratios (HRs) for event-free survival and overall survival. Sensitivity analysis and trial sequential analysis were conducted to further consolidate pooled results.

RESULTS

Among 4 eligible studies that were included, there were 3 randomized clinical trials and 1 controlled study. A total of 278 patients were allocated to the experimental group (ie, platinum-based chemotherapy plus STS; 158 patients, including 13 patients using contralatral ears of the control group as samples) or the control group (ie, chemotherapy; 133 patients, including 13 patients using contralateral ears of the experimental group as samples). Overall, patients who received STS had a statistically significantly decreased risk of ototoxic effects during the course of platinum-based chemotherapy (RR, 0.61; 95% CI, 0.49-0.77; P < .001; I2 = 5.0%) without a statistically significant increase in the risk of poor event-free survival (HR, 1.13; 95% CI, 0.70-1.82; P = .61; I2 = 0%) or overall survival (HR, 1.90; 95% CI, 0.90-4.03; P = .09; I2 = 0%). In the trial sequential analysis of event-free survival (z = -0.52) and overall survival (z = -1.68), although the cumulative z curves did not surpass the traditional significance boundary (-1.96 to 1.96 for both) or sequential monitoring boundary (event-free survival: -8.0 to 8.0; overall survival boundary not renderable in the analysis because the information size was too small) of the adjusted CI, they did not reach the required information size.

CONCLUSIONS AND RELEVANCE

This meta-analysis found that concurrent STS delivery was associated with a decreased risk of platinum-induced ototoxic effects among patients treated with platinum-induced chemotherapy. These findings suggest that concurrent STS for protection against ototoxic effects should be considered for patients indicated for platinum-based chemotherapy.

Synergistic Anti-cancer Activity of MH-30 in a Murine Melanoma Model Treated With Cisplatin and its Alleviated Effects Against Cisplatin-induced Toxicity in Mice

BACKGROUND/AIM

Although cisplatin is an effective anticancer drug, its toxic effects on normal tissues limit its use. We developed a herbal formula, MH-30, with increased fat-soluble polyphenols by improving the manufacturing method of HemoHIM. In this study, we examined whether the combination of MH-30 with cisplatin exerts synergistic antitumor effect while it reduces cisplatin-induced toxicities.

MATERIALS AND METHODS

MH-30 was produced by adding the ethanol-insoluble fraction to its extract after decocting herbs in 30% ethanol and water. We used a melanoma-bearing mice model to investigate synergistic anticancer effects. The NK cell activity and cytokine levels were measured by Cr⁵¹-release assay and ELISA. The AST, ALT, BUN, and creatinine levels were estimated in the serum.

RESULTS

MH-30 effectively inhibited melanoma growth in vitro. Furthermore, MH-30 had a synergistic effect in combination with cisplatin on melanoma growth inhibition in vitro and in vivo. In melanoma-bearing mice, cisplatin alone decreased the activity of NK cells and the levels of IL-2 and IFN-γ, which were effectively restored by the combination of MH-30 with cisplatin. Combined treatment with MH-30 and cisplatin significantly inhibited the cisplatin-induced increase in the levels of AST, ALT, BUN, and creatinine.

CONCLUSION

Combination of MH-30 with cisplatin may be a beneficial anticancer treatment with reduced adverse effects.

Molecular mechanisms of cisplatin-induced nephrotoxicity: a balance on the knife edge between renoprotection and tumor toxicity

Background

Cisplatin (cis-diamminedichloroplatinum II, CDDP) is one of the most effective chemotherapeutic agents. However, its clinical use is limited due to the severe side effects, including nephrotoxicity and acute kidney injury (AKI) which develop due to renal accumulation and biotransformation of CDDP. The alleviation or prevention of CDDP-caused nephrotoxicity is currently accomplished by hydration, magnesium supplementation or mannitol-induced forced diuresis which is considered for high-dose CDDP-treated patients. However, mannitol treatment causes over-diuresis and consequent dehydration in CDDP-treated patients, indicating an urgent need for the clinical use of safe and efficacious renoprotective drug as an additive therapy for high dose CDDP-treated patients.

Main body

In this review article we describe in detail signaling pathways involved in CDDP-induced apoptosis of renal tubular cells, oxidative stress and inflammatory response in injured kidneys in order to pave the way for the design of new therapeutic approaches that can minimize CDDP-induced nephrotoxicity. Most of these molecular pathways are, at the same time, crucially involved in cytotoxic activity of CDDP against tumor cells and potential alterations in their function might mitigate CDDP-induced anti-tumor effects.

Conclusion

Despite the fact that many molecules were designated as potential therapeutic targets for renoprotection against CDDP, modulation of CDDP-induced nephrotoxicity still represents a balance on the knife edge between renoprotection and tumor toxicity.

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) for disseminated intra-abdominal malignancies in children-a single-institution experience

PURPOSE

Our purpose was to present our institutional experience with performing complete cytoreduction surgery and heated intraoperative chemotherapy (CRS-HIPEC) for children with disseminated intraabdominal malignancies, guided by a leading international center performing CRS-HIPEC in children.

METHODS

Retrospective chart review of all cases of CRS-HIPEC in children in our institution, examining diagnosis, preoperative management, operative management, postoperative treatment, short term outcome including length of stay and complications, and long term outcome including survival and recurrence of disease.

RESULTS

9 children underwent CRS-HIPEC over 48months. The mean age of the patients was 8years. Tumors were: rhabdomyosarcoma (RMS), mesothelioma, Sertoli-Leydig, desmoplastic small round cell tumor, colon carcinoma and Wilms' tumor. Most patients received intraperitoneal cisplatin. Short term outcome was very good with median length of hospital stay of 13days and low rate of complications. Seven patients were alive at last follow up. Five patients developed a recurrent disease. Recurrence was intraabdominal in two of these patients.

CONCLUSIONS

CRS-HIPEC for children with disseminated intraabdominal malignancies performed in a dedicated institution and with guidance by a leading international center can be performed safely.

TYPE OF STUDY

Treatment study.

LEVEL OF EVIDENCE

IV.

Pharmacokinetics of sodium thiosulfate in Guinea pig perilymph following middle ear application

Hypothesis

To determine the pharmacokinetics of sodium thiosulfate in the inner ear perilymph following middle ear application in Guinea pigs.

Background

Cisplatin chemotherapy is often associated with a dose-dependent high frequency sensorineural hearing loss. Sodium thiosulfate has been shown to reduce cisplatin-induced ototoxicity when given intravenously, but this may limit the tumoricidal effects of the chemotherapy. Recent animal studies looking at middle ear application of sodium thiosulfate have shown prevention of outer hair cell and hearing loss, but the perilymph pharmacokinetics have not yet been established.

Methods

Twenty Guinea pig ears were split into two groups and administered sodium thiosulfate to the middle ear at either a concentration of 250 mg/mL or 50 mg/mL for 30 min. Perilymph samples were then obtained serially through the round window over 6 h. Sodium thiosulfate concentrations were obtained using high-pressure liquid chromatography.

Results

The 250 mg/mL group had a maximum perilymph concentration of 7.27 mg/mL (±0.83) that decreased to 0.94 mg/mL (±0.03) over 6 h. The 50 mg/mL group had an initial concentration of 1.63 mg/mL (±0.17) and was undetectable after 1 h. The half-life of sodium thiosulfate within perilymph was 0.74 h.

Conclusions

and Relevance: The results of this study show that sodium thiosulfate is capable of diffusing through round window and into the inner ear perilymph. Peak levels decline over several hours after exposure. This has a potential application as a localized therapy in the prevention of cisplatin induced ototoxicity.

Tuning the metabolism of the anticancer drug cisplatin with chemoprotective agents to improve its safety and efficacy

Numerous in vivo studies have shown that the severe toxic side-effects of intravenously administered cisplatin can be significantly reduced by the co-administration of sulfur-containing 'chemoprotective agents'. Using a metallomics approach, a likely biochemical basis for these potentially useful observations was only recently uncovered and appears to involve the reaction of chemoprotective agents with cisplatin-derived Pt-species in human plasma to form novel platinum-sulfur complexes (PSC's). We here reveal aspects of the structure of two PSC's and establish the identification of an optimal chemoprotective agent to ameliorate the toxic side-effects of cisplatin, while leaving its antineoplastic activity largely intact, as a feasible research strategy to transform cisplatin into a safer and more effective anticancer drug.

Emerging Therapies for Sensorineural Hearing Loss

OBJECTIVE

To critically review and evaluate the proposed mechanisms and documented results of the therapeutics currently in active clinical drug trials for the treatment of sensorineural hearing loss.

DATA SOURCES

US National Institutes of Health (NIH) Clinical Trials registry, MEDLINE/PubMed.

STUDY SELECTION & DATA EXTRACTION

A review of the NIH Clinical Trials registry identified candidate hearing loss therapies, and supporting publications were acquired from MEDLINE/PubMed. Proof-of-concept, therapeutic mechanisms, and clinical outcomes were critically appraised.

DATA SYNTHESIS

Twenty-two active clinical drug trials registered in the United States were identified, and six potentially therapeutic molecules were reviewed. Of the six molecules reviewed, four comprised mechanisms pertaining to mitigating oxidative stress pathways that presumably lead to inner ear cell death. One remaining therapy sought to manipulate the cell death cascade, and the last remaining therapy was a novel cell replacement therapy approach to introduce a transcription factor that promotes hair cell regeneration.

CONCLUSION

A common theme in recent clinical trials registered in the United States appears to be the targeting of cell death pathways and influence of oxidant stressors on cochlear sensory neuroepithelium. In addition, a virus-delivered cell replacement therapy would be the first of its kind should it prove safe and efficacious. Significant challenges for bringing these bench-to-bedside therapies to market remain. It is never assured that results in non-human animal models translate to effective therapies in the setting of human biology. Moreover, as additional processes are described in association with hearing loss, such as an immune response and loss of synaptic contacts, additional pathways for targeting become available.

Effects of sodium thiosulfate versus observation on development of cisplatin-induced hearing loss in children with cancer (ACCL0431): a multicentre, randomised, controlled, open-label, phase 3 trial

BACKGROUND

Sodium thiosulfate is an antioxidant shown in preclinical studies in animals to prevent cisplatin-induced hearing loss with timed administration after cisplatin without compromising the antitumour efficacy of cisplatin. The primary aim of this study was to assess sodium thiosulfate for prevention of cisplatin-induced hearing loss in children and adolescents.

METHODS

ACCL0431 was a multicentre, randomised, open-label, phase 3 trial that enrolled participants at 38 participating Children's Oncology Group hospitals in the USA and Canada. Eligible participants aged 1-18 years with newly diagnosed cancer and normal audiometry were randomly assigned (1:1) to receive sodium thiosulfate or observation (control group) in addition to their planned cisplatin-containing chemotherapy regimen, using permuted blocks of four. Randomisation was initially stratified by age and duration of cisplatin infusion. Stratification by previous cranial irradiation was added later as a protocol amendment. The allocation sequence was computer-generated centrally and concealed to all personnel. Participants received sodium thiosulfate 16 g/m² intravenously 6 h after each cisplatin dose or observation. The primary endpoint was incidence of hearing loss 4 weeks after final cisplatin dose. Hearing was measured using standard audiometry and reviewed centrally by audiologists masked to allocation using American Speech-Language-Hearing Association criteria but treatment was not masked for participants or clinicians. Analysis of the primary endpoint was by modified intention to treat, which included all randomly assigned patients irrespective of treatment received but restricted to those assessable for hearing loss. Enrolment is complete and this report represents the final analysis. This trial is registered with ClinicalTrials.gov, number NCT00716976.

FINDINGS

Between June 23, 2008, and Sept 28, 2012, 125 eligible participants were randomly assigned to either sodium thiosulfate (n=61) or observation (n=64). Of these, 104 participants were assessable for the primary endpoint (sodium thiosulfate, n=49; control, n=55). Hearing loss was identified in 14 (28·6%; 95% CI 16·6-43·3) participants in the sodium thiosulfate group compared with 31 (56·4%; 42·3-69·7) in the control group (p=0·00022). Adjusted for stratification variables, the likelihood of hearing loss was significantly lower in the sodium thiosulfate group compared with the control group (odds ratio 0·31, 95% CI 0·13-0·73; p=0·0036). The most common grade 3-4 haematological adverse events reported, irrespective of attribution, were neutropenia (117 [66%] of 177 participant cycles in the sodium thiosulfate group vs 145 [65%] of 223 in the control group), whereas the most common non-haematological adverse event was hypokalaemia (25 [17%] of 147 vs 22 [12%] of 187). Of 194 serious adverse events reported in 26 participants who had received sodium thiosulfate, none were deemed probably or definitely related to sodium thiosulfate; the most common serious adverse event was decreased neutrophil count: 26 episodes in 14 participants.

INTERPRETATION

Sodium thiosulfate protects against cisplatin-induced hearing loss in children and is not associated with serious adverse events attributed to its use. Further research is needed to define the appropriate role for sodium thiosulfate among emerging otoprotection strategies.

FUNDING

US National Cancer Institute.

Cisplatin otoprotection using transtympanic L-N-acetylcysteine: a pilot randomized study in head and neck cancer patients

OBJECTIVES/HYPOTHESIS

To evaluate the feasibility and efficacy of transtympanic L-N-Acetylcysteine (L-NAC) administration in patients receiving cisplatin chemotherapy for head and neck cancer.

STUDY DESIGN

Prospective randomized nonblinded open-label clinical trial.

METHODS

Transtympanic 2% L-NAC was administered to one randomly selected ear with the other ear as control in each patient. Primary outcome parameter was the difference in the loss of pure tone averages (PTA) at 2, 4, and 8 kHz between the L-NAC and control ear at 1 to 2 months following chemotherapy.

RESULTS

Eleven patients completed the study, with two patients demonstrating significantly better hearing in the L-NAC treated ear (18.2%). However, for the overall group, the difference in hearing preservation did not reach significance. Two percent L-NAC administration was well tolerated in this patient population. There were no adverse effects associated with L-NAC.

CONCLUSION

Although the study did not demonstrate a significant benefit overall, transtympanic L-NAC was associated with significantly better hearing in two patients. Better delivery methods may improve the efficacy of this treatment. L-NAC remains a promising drug in preventing cisplatin-induced ototoxicity.

Can medical herbs stimulate regeneration or neuroprotection and treat neuropathic pain in chemotherapy-induced peripheral neuropathy?

Chemotherapy-induced neuropathy (CIPN) has a relevant impact on the quality of life of cancer patients. There are no curative conventional treatments, so further options have to be investigated. We conducted a systematic review in English and Chinese language databases to illuminate the role of medical herbs. 26 relevant studies on 5 single herbs, one extract, one receptor-agonist, and 8 combinations of herbs were identified focusing on the single herbs Acorus calamus rhizoma, Cannabis sativa fructus, Chamomilla matricaria, Ginkgo biloba, Salvia officinalis, Sweet bee venom, Fritillaria cirrhosae bulbus, and the herbal combinations Bu Yang Huan Wu, modified Bu Yang Huan Wu plus Liuwei Di Huang, modified Chai Hu Long Gu Mu Li Wan, Geranii herba plus Aconiti lateralis praeparata radix , Niu Che Sen Qi Wan (Goshajinkigan), Gui Zhi Jia Shu Fu Tang (Keishikajutsubuto), Huang Qi Wu Wu Tang (Ogikeishigomotsuto), and Shao Yao Gan Cao Tang (Shakuyakukanzoto). The knowledge of mechanism of action is still limited, the quality of clinical trials needs further improvement, and studies have not yielded enough evidence to establish a standard practice, but a lot of promising substances have been identified. While CIPN has multiple mechanisms of neuronal degeneration, a combination of herbs or substances might deal with multiple targets for the aim of neuroprotection or neuroregeneration in CIPN.

Cisplatin-induced nephrotoxicity and targets of nephroprotection: an update

Cisplatin is a highly effective antitumor agent whose clinical application is limited by the inherent nephrotoxicity. The current measures of nephroprotection used in patients receiving cisplatin are not satisfactory, and studies have focused on the investigation of new possible protective strategies. Many pathways involved in cisplatin nephrotoxicity have been delineated and proposed as targets for nephroprotection, and many new potentially protective agents have been reported. The multiple pathways which lead to renal damage and renal cell death have points of convergence and share some common modulators. The most frequent event among all the described pathways is the oxidative stress that acts as both a trigger and a result. The most exploited pathways, the proposed protective strategies, the achievements obtained so far as well as conflicting data are summarized and discussed in this review, providing a general view of the knowledge accumulated with past and recent research on this subject.

Mechanistic study of BNP7787-mediated cisplatin nephroprotection: modulation of human aminopeptidase N

PURPOSE

Previous studies from our laboratory have identified a role for gamma-glutamyl transpeptidase (GGT) in BNP7787 (disodium 2,2'-dithio-bis ethane sulfonate, dimesna, Tavocept™)-mediated cisplatin nephroprotection. Dekant has proposed that gamma-glutamyl transpeptidase (GGT), aminopeptidase N (APN) and cysteine-conjugate-β-lyase (CCBL) comprise a multi-enzyme pathway that acts on xenobiotic-glutathione conjugates converting them to nephrotoxic metabolites. We report modulation of APN activity within this pathway by BNP7787-derived mesna-disulfide heteroconjugates.

METHODS

A fluorimetric assay was used to determine the effect of BNP7787, BNP7787-derived mesna-disulfide heteroconjugates, and the BNP7787 metabolite, mesna (sodium 2-mercaptoethane sulfonate), on the initial velocity and overall progress curve of the human APN reaction in vitro.

RESULTS

Neither BNP7787 nor mesna-cysteinyl-glutamate inhibited human APN. Select BNP7787-derived mesna-disulfide heteroconjugates (mesna-cysteine, mesna-glutathione, mesna-cysteinyl-glycine) and high concentrations of mesna inhibited APN activity. Allosteric effects on the enzyme progress curve outside of the linear initial velocity region were observed for mesna-cysteinyl-glycine, mesna-glutathione and mesna-cysteinyl-glutamate and appeared to be a function of having both mesna and di- or tri-peptide functionalities in one molecule. In situ-generated mesna-cisplatin conjugates were not a substrate for human APN.

CONCLUSIONS

BNP7787-mediated prevention or mitigation of cisplatin-induced nephrotoxicity may involve APN inhibition by certain BNP7787-derived mesna-disulfide heteroconjugates and appears correlated to the presence of a glycinate moiety and/or an anionic group. Two general mechanisms for BNP7787-mediated nephroprotection of cisplatin-induced nephrotoxicity involving the GGT, APN and CCBL nephrotoxigenic pathway are proposed which acting in a concerted and/or synergistic manner, and thereby prevent or mitigate cisplatin-induced renal toxicity.

Mechanistic study of BNP7787-mediated cisplatin nephroprotection: modulation of gamma-glutamyl transpeptidase

PURPOSE

The mechanisms for cisplatin-induced renal cell injury have been the focus of intense investigation for many years with a view to provide a more effective and convenient form of nephroprotection. BNP7787 (disodium 2,2'-dithio-bis ethane sulfonate; dimesna, Tavocept), is a water-soluble disulfide investigational new drug that is undergoing clinical development for the prevention and mitigation of clinically important chemotherapy-induced toxicities associated with platinum-type chemotherapeutic agents. We hypothesized that part of BNP7787's mechanism of action (MOA) pertaining to the potential prevention of cisplatin-induced nephrotoxicity involves the inhibition of gamma-glutamyl transpeptidase (GGT) activity, mediated by BNP7787-derived mesna-disulfide heteroconjugates that contain a terminal gamma-glutamate moiety [e.g., mesna-glutathione (MSSGlutathione) and mesna-cysteinyl-glutamate (MSSCE)].

METHODS

Inhibition studies were conducted on human and porcine GGT to determine the effect of mesna-disulfide heteroconjugates on the enzyme's activity in vitro. These studies utilized a fluorimetric assay that monitored the hydrolysis of L-gamma-glutamyl-7-amino-4-trifluoromethylcoumarin (GG-AFC) to AFC.

RESULTS

Mesna-disulfide heteroconjugates that contained gamma-glutamyl moieties were potent inhibitors of human and porcine GGT. An in situ-generated mesna-cisplatin conjugate was not a substrate for GGT.

CONCLUSIONS

The GGT xenobiotic metabolism pathway is postulated to be a major toxification pathway for cisplatin nephrotoxicity, and BNP7787 may play a novel and critical therapeutic role in the modulation of GGT activity. We further postulate that there are two general mechanisms for BNP7787-mediated nephroprotection against cisplatin-induced nephrotoxicity involving this pathway. First, the active BNP7787 pharmacophore, mesna, produces an inactive mesna-cisplatin conjugate that is not a substrate for the GGT toxification pathway (GGT xenobiotic metabolism pathway) and, second, BNP7787-derived mesna-disulfide heteroconjugates may serve as selective, potent inhibitors of GGT, possibly resulting in nephroprotection by a novel means.

Ototoxicity in Children Receiving Platinum Chemotherapy: Underestimating a Commonly Occurring Toxicity That May Influence Academic and Social Development

Purpose

To describe the frequency and severity of ototoxicity in a series of pediatric patients treated with platinum-based chemotherapy.

Patients and Methods

Serial audiologic evaluations were conducted for 67 patients aged 8 months to 23 years who received platinum-based chemotherapy. Audiologic data was analyzed to determine time to hearing-loss using American Speech-Language-Hearing Association (ASHA) criteria, and the effects of treatment and patient characteristics on the incidence and severity of ototoxicity.

Results

Bilateral decreases in hearing were seen in 61% of patients (median time to hearing loss, 135 days). Children treated for medulloblastoma, osteosarcoma, and neuroblastoma had greater incidence and severity of hearing loss. Agreement between the usually reported National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) and ASHA criteria was inadequate.

Conclusion

Traditional reporting of toxicity data (CTCAE) has under-reported ototoxicity and minimized the significance of hearing loss in children. As pediatric patients experience improved survival, the effects and implications of high-frequency hearing loss with regard to academic achievement and speech and language development are important considerations, especially in patients younger than 5 years.

Ototoxic protection of sodium thiosulfate: daily vs constant infusion

OBJECTIVE

Compare the effect of a daily dose of sodium thiosulfate (STS) to continuous infusion of STS on Hartley albino guinea pig (HAGP) on cisplatin (CP)-induced sensorineural hearing loss. Study design Prospective randomized pilot study comparing a single daily dose of STS to a constant controlled infusion of STS given the middle ear space (MES) with an ototoxic regimen of CP. The hearing thresholds will be obtained by auditory brainstem response (ABR) 1 week before and after treatment. Treatment effects on responses at 2, 8, and 16 kHz signals will be investigated by an analysis of variance with one between subjects' condition and two within subjects' conditions.

SETTING

Basic science laboratory.

RESULTS

STS protection resulted in significantly less hearing loss post-treatment for the protected ears. Guinea pigs with continuous infusion of STS demonstrated less loss in the protected ear than those who received the single daily dose. As expected, hearing loss at 2 kHz was less than that at 8 and 16 kHz.

CONCLUSION

A continuous infusion of STS directly to the MES is better than a single daily dose of STS to the MES in reducing the ototoxicity of CP.

SIGNIFICANCE

Any targeted protection, whether by continuous infusion or daily dose, is better than no protection against the sensorineural hearing loss of CP.

Protection against cisplatin-induced ototoxicity by N-acetylcysteine in a rat model

Cisplatin (CDDP) is a widely used chemotherapeutic agent that is highly ototoxic. Animal studies and clinical trials have shown that thiosulfates can protect against platinum-induced ototoxicity. This study investigated a new model for CDDP ototoxicity in the rat, and tested the potential chemoprotective effect of administering N-acetylcysteine (NAC) before giving CDDP. Long Evans rats were treated with CDDP 6 mg/kg delivered to the aorta via a retrograde right external carotid artery infusion, 15 min after intravenous (IV) infusion of saline (n=8) or NAC 400 mg/kg (n=8), such that the vertebral arteries were perfused. Subsequent groups were similarly treated with NAC 30 min before (n=7) and 4 h after (n=7) CDDP. Auditory brainstem response (ABR) thresholds were tested at 4-20 kHz, 7 days after treatment and compared to baseline ABR values. The NAC-treated rats exhibited no significant change from baseline values at all time intervals, while the saline-treated rats showed marked ototoxicity, especially at higher frequencies. Furthermore, the rats treated with NAC 15 min before CDDP exhibited less overall toxicity to CDDP, as evidenced in weight loss 7 days post-treatment (mean for saline=-39.63 g; mean for NAC=-21.13 g; p=0.0084). These data show that treatment with NAC can prevent CDDP-induced ototoxicity in rats.

WR-2721 (Amifostine) ameliorates cisplatin-induced hearing loss but causes neurotoxicity in hamsters: dose-dependent effects

Chemoprotective agents reduce the toxic side effects of chemotherapy agents such as cisplatin. The conventional belief is that the chemoprotective agent WR-2721 (Amifostine), while protecting against most cisplatin-induced side effects, does not protect against cisplatin-induced ototoxicity (i.e., hearing loss). There is no knowledge, however, about the efficacy of high doses of WR-2721 (WR) in possibly protecting against cisplatin-induced ototoxicity. Thus, the dose-dependent effects of WR in possibly ameliorating cisplatin-induced ototoxicity were investigated. Hamsters were given a series of 5 cisplatin injections (3 mg/kg/injection once every other day, i.p.) either alone or in combination with 18, 40, 80, or 400 mg/kg/injection of the rescue agent WR ( n = 5 or 10/group). Other groups received either 80 mg/kg/injection WR alone ( n = 5) or were untreated ( n = 14). Ototoxicity was assessed by auditory brain stem responses (ABR). WR provided dose-dependent rescue from cisplatin's ototoxicity with no protection at the low dose of 18 mg/kg, moderate protection at 40 mg/kg, and nearly complete protection at 80 and 400 mg/kg. However, WR doses of 40 mg/kg or higher caused neurotoxicity as evidenced by prolongations in the ABR's interpeak latencies. Thus, high doses of WR provided the beneficial effect of protecting against cisplatin-induced ototoxicity, but had the harmful side effect of neurotoxicity. Previous failures to find chemoprotection from cisplatin-induced ototoxicity were likely due to the use of WR doses that were too small. The clinical implications of the beneficial and harmful effects of high doses of WR are discussed.

Local application of sodium thiosulfate prevents cisplatin-induced hearing loss in the guinea pig

Cisplatin (CDDP), an anticancer drug used extensively to treat a broad range of neoplasms, has strong ototoxic side effects. Sodium thiosulfate (STS) has been described as a protective agent against CDDP toxicity, but it also reduces CDDP's antitumoral cytotoxicity. To maintain the antitumoral effectiveness of systemic administration of CDDP, a strategy has been developed to apply STS directly into the cochlea. Perfusion of STS into the cochleae of guinea pigs completely prevented CDDP-induced hearing loss, with no change in either compound action potential (CAP) or distortion product otoacoustic emission (DPOAE) audiograms during the time course of the treatment. Histological analysis revealed a minimal loss of outer hair cells (OHCs) in the organ of Corti and no damage to the marginal cells of the stria vascularis as seen in animals exposed to CDDP. Cytocochleograms prepared 6 days after CDDP exposure showed that STS treatment protected more than 92.8% of OHCs and IHCs destined to die. Furthermore, it prevented CDDP-induced mitochondrial damage and subsequent translocation of cytochrome c, DNA fragmentation, and suppressed the apoptotic and necrotic hair cell degeneration. These results suggest that local application of STS may be an interesting strategy to prevent CDDP ototoxicity in patients undergoing CDDP chemotherapy.

Effects of trolox, locally applied on round windows, on cisplatin-induced ototoxicity in guinea pigs

OBJECTIVE

Cisplatin (CDDP), an antitumor agent widely used in the treatment of pediatric solid tumors, has dose-limiting side effects such as ototoxicity and nephrotoxicity. Recently, evidence has been accumulated to demonstrate that these side effects are closely related to oxidative stress. In the present study, we attempted to suppress CDDP-induced ototoxicity in guinea pigs by administering trolox, a water-soluble analogue of alpha-tocopherol which is a natural lipid-soluble antioxidant, locally on round windows.

METHODS

Hartley albino guinea pigs (250-300 g) were treated with CDDP (0.3 mg/ml) in the presence or absence of a combined treatment of trolox (5 mM). Both drugs were administered locally on round windows.

RESULTS

The combined treatment of trolox distinctly improved the ototoxic side effects induced by CDDP. These were: elevation of auditory brain stem response threshold at 4, 8 and 16 kHz and substantial losses of outer hair cells with the base-to-apex gradient.

CONCLUSION

Trolox, locally applied on round windows, showed a suppression on CDDP-ototoxicity. The results obtained in the present study suggest that a local application of trolox in the tympanic cavity can be a promising candidate to prevent the CDDP-ototoxicity in the future.

Cisplatin-induced hyperactivity in the dorsal cochlear nucleus and its relation to outer hair cell loss: relevance to tinnitus

Cisplatin causes both acute and chronic forms of tinnitus as well as increases in spontaneous neural activity (hyperactivity) in the dorsal cochlear nucleus (DCN) of hamsters. It has been hypothesized that the induction of hyperactivity in the DCN may be a consequence of cisplatin's effects on cochlear outer hair cells (OHCs); however, systematic studies testing this hypothesis have yet to appear in the literature. In the present investigation, the relationship between hyperactivity and OHC loss, induced by cisplatin, was examined in detail. Hamsters received five treatments of cisplatin at doses ranging from 1.5 to 3 mg. kg(-1). day(-1), every other day. Beginning 1 mo after initiation of treatment, electrophysiological recordings were carried out on the surface of the DCN to measure spontaneous multiunit activity along a set of coordinates spanning the medial-lateral (tonotopic) axis of the DCN. After recordings, cochleas were removed and studied histologically using a scanning electron microscope. The results revealed that cisplatin-treated animals with little or no loss of OHCs displayed levels of activity similar to those seen in saline-treated controls. In contrast, the majority (75%) of cisplatin-treated animals with severe OHC loss displayed well-developed hyperactivity in the DCN. The induced hyperactivity was seen mainly in the medial (high-frequency) half of the DCN of treated animals. This pattern was consistent with the observation that OHC loss was distributed mainly in the basal half of the cochlea. In several of the animals with severe OHC loss and hyperactivity, there was no significant damage to IHC stereocilia nor any observable irregularities of the reticular lamina that might have interfered with normal IHC function. Hyperactivity was also observed in the DCN of animals showing severe losses of OHCs accompanied by damage to IHCs, although the degree of hyperactivity in these animals was less than in animals with severe OHC loss but intact IHCs. These results support the view that loss of OHC function may be a trigger of tinnitus-related hyperactivity in the DCN and suggest that this hyperactivity may be somewhat offset by damage to IHCs.

Round window application of D-methionine provides complete cisplatin otoprotection

OBJECTIVE

Cisplatin is a widely used, very effective chemotherapeutic agent that can cause severe ototoxicity. In this study, D-methionine was tested as an otoprotectant via round window membrane (RWM) application in the chinchilla.

METHODS

A minute amount of cisplatin alone, or D-methionine followed by cisplatin, was applied topically directly to the intact RWM of anesthetized adult chinchillas. Auditory brainstem responses were measured before and 1 week after topical round window application. Animals were killed, and the cochleas were examined.

RESULTS

The ears pretreated with D-methionine were completely protected from hearing loss and hair cell loss in the organ of Corti compared with controls. The ears receiving cisplatin without D-methionine protection sustained nearly complete hearing loss with threshold shifts of >60 dB, with extensive outer hair cell loss throughout the organ of Corti but particularly in the basal turn.

CONCLUSION

These results demonstrate that topical D-methionine provides excellent otoprotection against cisplatin-induced ototoxicity both electrophysiologically and structurally.

Increases in spontaneous neural activity in the hamster dorsal cochlear nucleus following cisplatin treatment: a possible basis for cisplatin-induced tinnitus

Recent investigations in the hamster have implicated increased spontaneous activity (SA) in the dorsal cochlear nucleus (DCN) as a contributing factor in the etiology of tinnitus induced by intense sound exposure. It might therefore be expected that increased SA would also develop in the DCN of hamsters treated with cisplatin, another cause of tinnitus. We tested this hypothesis by measuring the effects of cisplatin on SA in the DCN. Adult hamsters were divided into three groups, each receiving five injections of cisplatin at one of the following doses: 3 mg/kg, 2.25 mg/kg, or 1.5 mg/kg. Each group had corresponding controls receiving injections of isotonic saline. The effects of cisplatin were studied electrophysiologically 1 month after treatment by recording multiunit SA on the surface of the DCN. Measurements of SA were obtained in three rows of 13-15 locations spaced roughly 100 microm apart and spanning the length of the DCN along the tonotopic axis. Effects of cisplatin were evaluated by comparing plots of mean SA vs. tonotopic locus for cisplatin-treated groups with those of their corresponding untreated control groups. The results demonstrated a consistently higher level of SA in cisplatin-treated groups than in untreated controls. Whereas the highest rates of mean SA in control groups were between 10 and 15 events/s, the highest mean spontaneous rates in cisplatin-treated groups were between 25 and 38 events/s. The cisplatin-induced hyperactivity was greatest in the medial half of the DCN corresponding to the high frequency portion of the tonotopic range. These results suggest that cisplatin treatment is an effective inducer of hyperactivity in the DCN. This hyperactivity may be an important neural correlate of cisplatin-induced tinnitus.

Perilymphatic application of cisplatin over several days in albino guinea pigs: dose-dependency of electrophysiological and morphological effects

Cisplatin, at 0, 3, 30 or 300 microg/ml in saline, was applied to the scala tympani of the cochlea of guinea pigs via osmotic mini-pumps, operating at a pump rate of 0.5 microl/h. Electrocochleographic recordings were made from an implanted round window electrode. When an electrocochleographic criterion of ototoxicity was reached (40 dB loss in compound action potential (CAP) threshold at 8 kHz), or after 1 week if this criterion was not reached, the animals were sacrificed for light microscopy. A subgroup of animals had endocochlear potentials (EPs) measured prior to sacrifice. Hearing remained stable in the 0 microg/ml control group, but a sudden drop of auditory sensitivity across the whole frequency range was observed in all other groups. It took 1-5 days before the drop occurred, dependent on cisplatin concentration. CAP and cochlear microphonics were lost simultaneously. The EP was severely depressed in the affected animals, suggesting that cisplatin effects on the EP are primary. However, histology revealed an accompanying loss of outer hair cells, primarily in the basal turn. It is concluded that if cisplatin is given until ototoxicity becomes apparent electrophysiologically, then the cochlear pathology from intrascalar cisplatin administration resembles that from daily parenteral administration at 1.5-2.0 mg/kg. The cochlear pathology from the parenteral treatment was greater than that observed with 30 microg/ml pumps, and less than that from 300 microg/ml pumps.

Effects of alpha-tocopherol on cisplatin-induced ototoxicity in guinea pigs

Cisplatin (CDDP), an antitumor agent widely used in the treatment of head and neck cancers, has dose-limiting side effects such as ototoxicity and nephrotoxicity. Recently, evidence has been accumulated to demonstrate that these side effects are closely related to oxidative stress. In the present study, we attempted to suppress CDDP-induced ototoxicity and nephrotoxicity in guinea pigs by administering alpha-tocopherol, a naturally occurring antioxidant. Hartley albino guinea pigs (250 approximately 300 g) were treated with CDDP (4 mg/kg intraperitoneally (I.P.)) for 3 days in the presence and absence of alpha-tocopherol (50 mg/kg I.P.) injection for 6 days. The combined treatment of animals with alpha-tocopherol distinctly improved the CDDP-induced side effects. These were: loss of Preyer's reflex at high frequencies; distinct elevation of auditory brain stem response threshold at 16 kHz; increased lipid peroxidation in the cochlea determined by the malondialdehyde-thiobarbituric acid method; substantial losses of outer hair cells in the basal and second turns of the cochlea; fragmentation of nuclear DNA detected by the TUNEL method in cochlear hair cells and cells in the stria vascularis; and increases in serum BUN and Cr. These results strongly suggest that alpha-tocopherol suppresses CDDP-induced ototoxicity and nephrotoxicity via the suppression of the increased production of reactive oxygen species.

Histological effects of co-administration of an ACTH((4-9)) analogue, ORG 2766, on cisplatin ototoxicity in the albino guinea pig

Cisplatin is one of the most potent antineoplastic drugs presently known, but its therapeutic efficacy is seriously limited by several side effects such as ototoxicity. Several compounds that are known for their nephroprotective effects also seem to reduce the incidence and severity of cisplatin-induced ototoxicity. Hamers et al. (1994) and De Groot et al. (1997) investigated the possibly protective effect of concomitant administration of the ACTH((4-9)) analogue ORG 2766 upon cisplatin ototoxicity in guinea pigs. Animals were treated with cisplatin at a daily dose of 2.0 mg/kg for 8 consecutive days and ORG 2766 at a daily dose of 75 mcg/kg for 9 days. Concomitant administration of cisplatin plus ORG 2766 resulted in a bimodal distribution of the electrophysiological data (compound action potential and cochlear microphonics amplitudes) and the histological data (outer hair cell (OHC) counts). It was surmised that this dichotomy might occur at a certain cisplatin dose. We investigated whether this protective effect of ORG 2766 could be enhanced by reducing the daily dose of cisplatin while maintaining the same dose of ORG 2766. Thirty-six animals were treated with daily i.p. injections of cisplatin at a dose of 1.0 mg/kg (n=18) or 1.5 mg/kg (n=18) for 8 consecutive days. When comparing the mean OHC counts of the different experimental groups, treatment with cisplatin at a daily dose of 1.5 mg/kg for 8 consecutive days resulted in a considerable loss of OHCs, which was significantly reduced after co-administration of ORG 2766. Co-treatment with ORG 2766 did not result in a change in the volume of the scala media. The present results are in agreement with the electrophysiological results published earlier (Stengs et al., 1998b).

Cisplatin-induced hearing loss: influence of the mode of drug administration in the guinea pig

Cisplatin (8 mg/kg) was given intravenously to guinea pigs either as a 15 s bolus injection (25 animals) or as a 1 h infusion (28 animals). To determine the influence of the mode of cisplatin administration and pharmacokinetics on the ototoxic side-effect, the concentrations of cisplatin and the biotransformation product monoaquated cisplatin were determined in blood ultrafiltrate using liquid chromatography with post-column derivatization. Ototoxic effect was evaluated as difference in pre- and 96 h post-exposure auditory brainstem response (ABR) threshold. The cisplatin peak concentration was considerably higher, 19.2+/-2.4 microg/ml, in the bolus injection group than in the infusion group, 6.7+/-0.5 microg/ml (mean+/-S.E.M.). The area under the blood ultrafiltrate concentration time curve (AUC) for cisplatin was slightly greater in the infusion group, 442+/-26 microg/ml/min, than in the bolus injection group, 340+/-5 microg/ml/min. For monoaqua cisplatin, the AUC was not different between the groups (bolus injection: 30.8+/-1. 5 microg/ml/min, infusion: 34.1+/-3.3 microg/ml/min). A significant ototoxic effect was observed in both groups at 20 and 12.5 kHz, but there was no difference between the groups in the extent of threshold shift. The interindividual variability in susceptibility to ABR threshold shift was far greater than the variability in pharmacokinetics, suggesting that other factors are more important in determining the degree of hearing loss.

Application of antioxidants and other agents to prevent cisplatin ototoxicity

OBJECTIVE/HYPOTHESIS

To review the recent data from experiments performed in this laboratory to test the hypothesis that cisplatin ototoxicity is related to depletion of glutathione and antioxidant enzymes in the cochlea and that the use of antioxidants or protective agents would protect the cochlea against cisplatin damage and prevent hearing loss.

STUDY DESIGN/METHODS

Data were reviewed from experiments performed in this laboratory. Control rats were treated intraperitoneally with cisplatin 16 mg/kg. Experimental rats were given cisplatin in combination with one of the following protective agents: diethyldithiocarbamate, 4-methylthiobenzoic acid, ebselen, or lipoic acid. Animals in each group underwent auditory brainstem response (ABR) threshold testing before and 3 days after treatment. Cochleae were removed after final ABR testing and analyzed for glutathione and activities of the enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and malondialdehyde.

RESULTS

Rats in the control group receiving cisplatin were found to have significant ABR threshold shifts. This was accompanied by a reduction of glutathione and the activity of antioxidant enzymes (superoxide dismutase, glutathione peroxidase, catalase, and glutathione reductase) and an elevation of malondialdehyde. Experimental animals had preservation of ABR thresholds and levels of glutathione, antioxidant enzyme activity, and malondialdehyde that were similar to untreated animals.

CONCLUSION

Cisplatin ototoxicity appears to be initiated by fee-radical production, which causes depletion of glutathione and antioxidant enzymes in the cochlea, and lipid peroxidation, manifested by an increase in malondialdehyde. These effects were blocked by each of a series of antioxidant compounds given in combination with cisplatin. A mechanism for cisplatin ototoxicity is elaborated with a proposed plan of chemoprevention using agents with different mechanisms of action. These substances could be used alone or in combination to reduce the severity of cisplatin ototoxicity in patients.

Cytoprotection in the treatment of pediatric cancer: review of current strategies in adults and their application to children

BACKGROUND

The protection of patients from the acute and/or chronic toxicity of antineoplastic therapy has become a major concern of oncology centers around the world. However, most of the effort has been directed toward the adult population, and limited studies have been performed in the group that may gain the most from such strategies, namely, children.

PROCEDURES

The MedLine and CancerLit databases were surveyed, and the relevant biomedical literature on cytoprotection during antineoplastic treatment was analyzed.

RESULTS

Cytotoxicity from antineoplastic therapy customarily is addressed by altering dosing schedules, a technique that can seriously impact the efficacy of the therapy. Colony stimulating factors have been used posttherapy to stimulate recovery from neutropenia, and various agents have been proposed as pretherapy cytoprotectors. Trials in adults have produced mixed results, and, to date, only amifostine and dexrazoxane have been approved as cytoprotectors for very narrow indications. Few trials have been performed in children, although these patients often can look forward to long-term remission.

CONCLUSIONS

To prevent permanent toxicities from antineoplastic therapies that impact long-term pediatric survivors, the experience gained in adults should be extended more aggressively to children, and formal, randomized trials should be performed to determine the type of protection most suitable for the pediatric population.

Protective effects of a neurotrophic ACTH(4-9) analog on cisplatin ototoxicity in relation to the cisplatin dose: an electrocochleographic study in albino guinea pigs

Cisplatin is a potent cell cycle non-specific chemotherapeutic agent that produces side effects including high-frequency hearing loss. Hamers et al. (1994) studied electrophysiologically the effect of an ACTH(4-9) analog, also known as ORG2766, on the ototoxicity of cisplatin (administered at 2 mg/kg/day for 8 days) in guinea pigs. ORG2766 was given concomitantly with cisplatin during the 8 day period and an additional dose was given on day 9. The conclusion of this study was that ORG2766 might partially prevent cisplatin ototoxicity, but that the chosen cisplatin dose (2 mg/kg/day; 8 days) might have been too high. Because of the high cisplatin dose the protective power of the co-treatment with ORG2766 might not have stretched to all animals. In this study the results of co-treatment with the same dose and daily schedule of ORG2766 and cisplatin doses of 1.0 mg/kg/day and 1.5 mg/kg/day for 8 days are presented. The measurements were performed over a broad range of frequencies (0.5-16 kHz). Electrocochleography was performed at day 10. In the 1.0 mg/kg/day group there was no beneficial effect of ORG2766, although a tendency towards a division between a subgroup resembling control animals and a subgroup with severe cisplatin effects was noted in the co-treated group. In the 1.5 mg/kg/day co-treated group three animals showed compound action potential (CAP) amplitudes close to those of the controls at all frequencies except the very highest (12 and 16 kHz), the remaining three had CAP amplitudes comparable to those of animals in the cisplatin alone group. The effect of ORG2766 on the latter group of six animals taken together was statistically significant. The dichotomy in the results for the 1.5 mg/kg/day group co-treated with ORG2766 suggests that ORG2766 may have a protective effect against cisplatin ototoxicity which, however, depends on a factor currently unknown.

Comparison of Five Agents in Protecting the Cochlea Against the Ototoxic Effects of Cisplatin in the Hamster

The purpose of this investigation was to study the ameliorating effects of four agents on cis-platin-induced ototoxicity. Hamsters were given a series of five cisplatin injections either alone or in combination with sodium thiosulfate (STS), diethyldihydrothiocarbamate (DDTC), and S-2(3-aminopropylamino) ethylphosphorothiolc acid (WR-2721), or fosfomycin. Ototoxicity was assessed anatomically by quantifying the extent of cochlear damage with the scanning electron microscope and physiologically with measures of the auditory brain stem response. When administered alone, cisplatin induced widespread loss of outer hair cells (OHCs) along much of the cochlea in the hamster, especially in the basal and middle turns, with an average survival of only 56% of the OHC population. In contrast, inner hair cells resisted cisplatin ototoxicity in the hamster. Thus the ameliorative effects of the different test agents were assessed by counting the number of surviving OHCs in each treatment group and comparing with cisplatin-treated controls. STS provided the most effective protection against the ototoxic effects of cisplatin, yielding 91% survival of OHCs. DDTC also reduced the ototoxic effects of cisplatin, yielding 68% survival of OHCs. Cotreatment with WR-2721 and fosfomycin yielded 45% and 52% OHC survival, respectively, and thus did not provide any chemoprotection. The results closely paralleled those based on auditory brain stem response recordings in that the magnitude of threshold shift was proportional to the amount of OHC loss; also, the amount of threshold shift at each frequency was in good agreement with the pattern of hair cell loss along the cochlear spiral. Thus both histologic and physiologic results suggest that STS and DDTC hold promise for ameliorating the ototoxic effects of cisplatin chemotherapy.

Protection by 4-methylthiobenzoic acid against cisplatin-induced ototoxicity: antioxidant system

This study was undertaken in order to determine the changes in auditory brainstem-evoked responses relationship with the changes in the levels of GSH, lipid peroxidation and antioxidant enzymes activity in cisplatin-induced ototoxicity and otoprotection by 4-methylthiobenzoic acid (MTBA). Male Wistar rats in different groups were treated as follows: 1) saline control; 2) cisplatin (16 mg/kg, intraperitoneally); 3) MTBA (250 mg/kg, intraperitoneally), and 4) cisplatin plus MTBA. Post-treatment auditory brainstem-evoked responses were performed after three days and the rats were sacrificed and cochleae harvested. The cochleae were analyzed for glutathione (GSH), antioxidant enzyme activity, and malondialdehyde levels. The cisplatin injected rats showed a threshold elevation of 31.9 +/- 16.0 dB above the pretreatment thresholds using click stimulus. Rats treated with MTBA plus cisplatin did not show significant elevation of hearing threshold. Cisplatin plus MTBA administration showed a higher levels of cochlear GSH (5.59 +/- 0.35 nmoles/mg protein) compared to cisplatin alone (4.46 +/- 0.13 nmoles/mg protein). Cisplatin treated rats showed a decrease in superoxide dismutase, catalase, glutathione peroxidase (GSH-peroxidase), and glutathione reductase (GSH-reductase) activities (57%, 83%, 78% and 58% of control). Cochlear superoxide dismutase, catalase and GSH-reductase activities and MDA levels were restored in the rats injected with cisplatin plus MTBA, compared to cisplatin alone. It is concluded that the protection conferred by MTBA against cisplatin ototoxicity is associated with sparing of the cochlear antioxidant system.

Phase II evaluation of cisplatin and WR2721 for refractory metastatic breast cancer

Cisplatin, as second-line therapy for metastatic breast cancer (MBC), has at best shown only modest response rates. At high doses, the toxicity profile of this drug may outweigh any potential benefits for MBC patients. We performed a phase II study to determine whether the investigational agent WR2721 would mitigate the toxicity of cisplatin in patients with MBC and to assess the antitumor response of cisplatin as salvage therapy. Thirteen women were enrolled in the study. Cisplatin was administered at a dose of 120 mg/m2 together with WR2721 at a dose of 910 mg/m2 intravenously every 21 days. Response was assessed at the end of two cycles, and toxicity was evaluated after each treatment cycle. No objective antitumor responses were noted. Three patients exhibited toxicity from cisplatin in the form of ototoxicity, nephrotoxicity, myelotoxicity, and persistent delayed nausea and vomiting necessitating discontinuation from the study. There was one death from renal failure. WR2721 itself caused significant but transient hypotension in 46% of the patients. In our experience, salvage chemotherapy with cisplatin in pretreated patients with MBC produced no objective responses. WR2721 did not prevent the occurrence of organ toxicity.

The effect of sodium thiosulfate on ototoxicity and pharmacokinetics after cisplatin treatment in guinea pigs

The effect of sodium thiosulfate (STS) on the pharmacokinetics and ototoxicity of cisplatin (CDDP) was investigated in guinea pigs. Animals received three intramuscular injections of 7.5 mg/kg CDDP separated by intervals of 5 days with or without STS (1,000 mg/kg) administered intraperitoneally immediately and 1 h after each injection of CDDP or 3 and 6 h later. When administered alone, CDDP caused total outer hair cell (OHC) loss in the basal and second turns of the cochlea. In the group administered CDDP and STS, damage to the OHCs was mild when STS was given concurrently, but was severe when STS was given 3 and 6 h later. Pharmacokinetics measured as free and total platinum (Pt) concentrations in plasma and total Pt concentration in perilymph was not affected after administration of STS with CDDP. These results suggest that an inactive Pt-thiosulfate complex is formed in plasma and is measured as a free Pt component which enters the perilymph via the blood-cochlear barrier. Two possible mechanisms are proposed by which STS reduces ototoxicity: entry of CDDP into target cells such as OHCs and strial marginal cells or binding to intracellular macromolecules of these cells is prevented.

Carboplatin combined with amifostine, a bone marrow protectant, in the treatment of non-small-cell lung cancer: a randomised phase II study

Amifostine (WR-2721), a thiol compound, has been shown to protect normal tissue from alkylating agents and cisplatin-induced toxicity without loss of anti-tumour effects. To confirm this result, we conducted a phase II randomised trial to determine if the addition of amifostine reduces the toxicity of carboplatin without loss of anti-tumour activity in patients with inoperable non-small-cell lung cancer (NSCLC). After the first course of carboplatin (600 mg m-2 i.v. infusion), 21 patients were randomised to receive three cycles of carboplatin alone (C arm) or three infusions of amifostine at 910 mg m-2 (CA arm) at 28 day intervals. The amifostine was given 20 min before and at 2 and 4 h after carboplatin. Since the 910 mg m-2 amifostine infusion led to hypotension in six patients, the dosage was reduced by 25%, to 683 mg m-2 t.i.d., in the other four patients. Amifostine was well tolerated at this dose level. Five patients in the CA arm and three in the C arm had their planned treatment discontinued owing to progressive disease (n = 3), amifostine side-effects (hypotension, sneezing and sickness, n = 4), and carboplatin-induced thrombocytopenia (n = 1). Bone marrow and renal function at study entry and after the first course of carboplatin before randomisation were similar in both treatment arms. Twenty courses of carboplatin+amifostine have been compared with 25 courses of carboplatin alone. Although there was no statistically significant difference with respect to haematological values comparing both arms, the median time to platelet recovery (> 100 x 10(9) l-1) (13.5 days vs 21 days; P = 0.04) and the need for hospitalisation for i.v. antibiotic and other supportive treatment tended to be reduced in the CA arm (0/20 vs 6/25 patient courses; P = 0.06). Response rates and median survival (14 vs 9 months) were no different, excluding tumour protection activity by amifostine. These results with a small number of patients suggest that amifostine given with carboplatin may reduce the duration of thrombocytopenia and hospitalisation.

The comparative effects of sodium thiosulfate, diethyldithiocarbamate, fosfomycin and WR-2721 on ameliorating cisplatin-induced ototoxicity

The efficacies of four agents in ameliorating cisplatin-induced ototoxicity were investigated. Hamsters were given a series of 5 cisplatin injections (3 mg/kg/injection once every other day, i.p.) either alone or in combination with 1600 mg/kg/injection sodium thiosulfate (STS), 300 mg/kg/injection diethyldithiocarbamate (DDTC), 18 mg/kg/injection WR-2721, or 300 mg/kg/injection fosfomycin (n = 10/group). Ototoxicity was assessed electrophysiologically by auditory brainstem responses (ABRs) and anatomically by cochlear histology. The greatest auditory protection was given by STS, followed by DDTC. WR-2721 and fosfomycin did not provide any protection. All of the animals in the STS and DDTC groups survived, while some fatalities occurred in the fosfomycin, WR-2721, and cisplatin-only groups. Thus, the agents that were protective against ototoxicity were also protective against mortality. The ABRs also provided evidence of cisplatin-induced neuropathy. In summary, STS and DDTC hold promise for ameliorating the ototoxic effects of cisplatin chemotherapy and the hamster proved to be an excellent model of cisplatin ototoxicity.