Characterization and Multiparameter Analysis of Visual Adverse Events in Irofulven Single-Agent Phase I and II Trials

Antroxazole A, an oxazole-containing chamigrane dimer from the fungus Antrodiella albocinnamomea with immunosuppressive activity

Antroxazole A (1), a chamigrane type sesquiterpene dimer containing an oxazole moiety, has been characterized from cultures of the fungus Antrodiella albocinnamomea. The structure with absolute configuration was determined by extensive spectroscopic methods and single crystal X-ray diffraction. A plausible biosynthetic pathway for 1 was proposed. Compound 1 exhibits inhibition specifically against the LPS-induced proliferation of B lymphocyte cells with an IC₅₀ value of 16.3 μM.

Prostaglandin Reductase 1 as a Potential Therapeutic Target for Cancer Therapy

Altered tumor metabolism is a hallmark of cancer and targeting tumor metabolism has been considered as an attractive strategy for cancer therapy. Prostaglandin Reductase 1 (PTGR1) is a rate-limiting enzyme involved in the arachidonic acid metabolism pathway and mainly responsible for the deactivation of some eicosanoids, including prostaglandins and leukotriene B4. A growing evidence suggested that PTGR1 plays a significant role in cancer and has emerged as a novel target for cancer therapeutics. In this review, we summarize the progress made in recent years toward the understanding of PTGR1 function and structure, highlight the roles of PTGR1 in cancer, and describe potential inhibitors of PTGR1. Finally, we provide some thoughts on future directions that might facilitate the PTGR1 research and therapeutics development.

Targeting Germline- and Tumor-Associated Nucleotide Excision Repair Defects in Cancer

PURPOSE

Nucleotide excision repair (NER) gene alterations constitute potential cancer therapeutic targets. We explored the prevalence of NER gene alterations across cancers and putative therapeutic strategies targeting these vulnerabilities.

EXPERIMENTAL DESIGN

We interrogated our institutional dataset with mutational data from more than 40,000 patients with cancer to assess the frequency of putative deleterious alterations in four key NER genes. Gene-edited isogenic pairs of wild-type and mutant ERCC2 or ERCC3 cell lines were created and used to assess response to several candidate drugs.

RESULTS

We found that putative damaging germline and somatic alterations in NER genes were present with frequencies up to 10% across multiple cancer types. Both in vitro and in vivo studies showed significantly enhanced sensitivity to the sesquiterpene irofulven in cells harboring specific clinically observed heterozygous mutations in ERCC2 or ERCC3. Sensitivity of NER mutants to irofulven was greater than to a current standard-of-care agent, cisplatin. Hypomorphic ERCC2/3-mutant cells had impaired ability to repair irofulven-induced DNA damage. Transcriptomic profiling of tumor tissues suggested codependencies between DNA repair pathways, indicating a potential benefit of combination therapies, which were confirmed by in vitro studies.

CONCLUSIONS

These findings provide novel insights into a synthetic lethal relationship between clinically observed NER gene deficiencies and sensitivity to irofulven and its potential synergistic combination with other drugs.See related commentary by Jiang and Greenberg, p. 1833.

Sesquiterpenoids from Cultures of the Basidiomycetes Irpex lacteus

Eight previously undescribed sesquiterpenoids, tremutins A-H (1-8), together with three known ones (9-11), were isolated from cultures of the basidiomycetes Irpex lacteus. Structures of the new compounds together with absolute configurations were elucidated on the basis of extensive spectroscopic methods, as well as single-crystal X-ray diffractions and equivalent circulating density calculations. Compounds 1 and 2 possess an unusual 6/7-fused ring system that might be derived from a tremulane framework. Compounds 3-7 and 9-11 are tremulane sesquiterpenoids of which 4 and 5 are the first tremulane examples with a 1,2-epoxy moiety to be reported. Compounds 6, 7, 10, and 11 possess weak activities to several human cancer cell lines. Compound 8 shows a weak inhibitory effect on NO production with a half maximal inhibitory concentration (IC₅₀) value of 22.7 μM. Compound 1 inhibits the lipopolysaccharide (LPS)-induced proliferation of B lymphocyte cells with an IC₅₀ value of 22.4 μM, while 2 inhibits concanavalin A (Con A)-induced T cell proliferation and LPS-induced B lymphocyte cell proliferation with IC₅₀ values of 16.7 and 13.6 μM, respectively.

Mushrooms: an emerging resource for therapeutic terpenoids

Mankind has always been fascinated with nature and have heavily explored natural products since the ancient times. Evolution of diseases led to research on synthetic structure, specificity and activity-guided treatment. To combat threats of new developing diseases and the deleterious side effects posed by modern therapy, researchers have once again looked back towards natural resources. Although plants have been the main source of natural drugs, lower fungi are being recently paid attention to. Among them, mushrooms have emerged as an under-explored yet immensely rich resource, especially for bioactive terpenoids. A lot of research is going on around the world with mushroom-derived terpenoids especially their medicinal properties, some of which have even been used in pre- and post-clinical studies. From the literatures that are available, it was found that mushroom terpenoids have activity against a wide range of diseases. In this review, we have summarized different mushroom-derived terpenoids and their therapeutic properties.

Safety of repeated administrations of ixabepilone given as a 3-hour infusion every other week in combination with irinotecan in patients with advanced malignancies

Epothilones are active tubulin-interacting agents that warrant combinations in clinical studies. This phase I combination study explored ixabepilone administered as a 3-h infusion followed by a 90-minute infusion irinotecan, on days 1 and 14 of every 28-day cycle. Forty-one patients received doses of ixabepilone and irinotecan ranging from 15-30 mg/m(2) and 120-180 mg/m(2) every 2 weeks for a total of 173 cycles, respectively. Dose limiting toxicities reported at doses 25 mg/m(2) ixabepilone and 180 mg/m(2) irinotecan consisted of acute grade 3 diarrhoea and asthenia, eventually associated with neutropenia and sepsis, and/or delayed grade 3 peripheral neuropathy. Therefore, the recommended doses were 20 mg/m(2) ixabepilone and 180 mg/m(2) irinotecan. At this dose level, acute side effects were neutropenia, anaemia, nausea-vomiting, diarrhoea, asthenia, and alopecia. Delayed neuropathy was mostly restricted to reversible grade I-II. Pharmacokinetic data suggested no drug-drug interaction. Five objective responses were observed in four patients with lung cancer and one unknown primary epidermoid carcinoma patient. In conclusion, toxicity including peripheral neuropathy was manageable at the recommended doses of 20 mg/m(2) ixabepilone combined with 180 mg/m(2) irinotecan on days 1 and 14 every 28 days. Promising antitumour activity was observed in patients with platinum-pretreated lung cancer.

A phase I and pharmacokinetic study of irofulven and capecitabine administered every 2 weeks in patients with advanced solid tumors

PURPOSE

To determine the maximum tolerated dose (MTD), recommended dose, dose limiting toxicities (DLT), safety and pharmacokinetics of irofulven combined with capecitabine in advanced solid tumor patients.

EXPERIMENTAL DESIGN

Irofulven was given i.v. over 30 min on days 1 and 15 every 4 weeks; capecitabine was given orally twice daily, day 1 to 15. Dose levels (DL) were: irofulven (mg/kg)/capecitabine (mg/m2/day): DL1: 0.3/1,700; DL2: 0.4/1,700; DL3: 0.4/2,000; DL4: 0.5/2,000.

RESULTS

Between May 2002 and March 2004, 37 patients were treated and 36 evaluable for MTD. DLT occurred in 1/6 evaluable patients in DL1 (grade 3 thrombocytopenia); 1/6 in DL3 (grade 3 thrombocytopenia); 2/7 in DL4 (grade 3 febrile neutropenia, grade 3 thrombocytopenia). DL4 was defined as the MTD and DL3 was established as the recommended dose (RD). DLTs occurred in 1 of 14 additional patients treated at DL3. No treatment-related deaths or grade 4 non-hematological toxicity occurred, and grade 3 toxicities were infrequent. Antitumor activity was observed; two partial responses were noted in thyroid carcinoma (DL1, DL4); one unconfirmed partial response was observed in a patient with nasopharyngeal carcinoma, (DL3); 12 patients had disease stabilization >3 months; of eight patients with hormone refractory prostate cancer (HRPC), one patient had PSA normalization and four short-term stabilizations of PSA occurred. Capecitabine and irofulven pharmacokinetics results did not suggest drug-drug interactions.

CONCLUSIONS

Irofulven with capecitabine was adequately tolerated and evidence of antitumor activity was observed. The recommended dose is irofulven 0.4 mg/kg and capecitabine 2,000 mg/m2/day.

Depurinating acylfulvene-DNA adducts: characterizing cellular chemical reactions of a selective antitumor agent

Acylfulvenes (AFs) are a class of semisynthetic agents with high toxicity toward certain tumor cells, and for one analogue, hydroxymethylacylfulvene (HMAF), clinical trials are in progress. DNA alkylation by AFs, mediated by bioreductive activation, is believed to contribute to cytotoxicity, but the structures and chemical properties of corresponding DNA adducts are unknown. This study provides the first structural characterization of AF-specific DNA adducts. In the presence of a reductive enzyme, alkenal/one oxidoreductase (AOR), AF selectively alkylates dAdo and dGuo in reactions with a monomeric nucleoside, as well as in reactions with naked or cellular DNA, with 3-alkyl-dAdo as the apparently most abundant AF-DNA adduct. Characterization of this adduct was facilitated by independent chemical synthesis of the corresponding 3-alkyl-Ade adduct. In addition, in naked or cellular DNA, evidence was obtained for the formation of an additional type of adduct resulting from direct conjugate addition of Ade to AF followed by hydrolytic cyclopropane ring-opening, indicating the potential for a competing reaction pathway involving direct DNA alkylation. The major AF-dAdo and AF-dGuo adducts are unstable under physiologically relevant conditions and depurinate to release an alkylated nucleobase in a process that has a half-life of 8.5 h for 3-alkyladenine and less than approximately 2 h for dGuo adducts. DNA alkylation further leads to single-stranded DNA cleavage, occurring exclusively at dGuo and dAdo sites, in a nonsequence-specific manner. In AF-treated cells that were transfected with either AOR or control vectors, the DNA adducts identified match those from in vitro studies. Moreover, a positive correlation was observed between DNA adduct levels and cell sensitivity to AF. The potential contributing roles of AOR-mediated bioactivation and adduct stability to the cytotoxicity of AF are discussed.

A phase I and pharmacokinetic study of irofulven and cisplatin administered in a 30-min infusion every two weeks to patients with advanced solid tumors

BACKGROUND

To determine maximum tolerated dose (MTD), recommended dose, safety and pharmacokinetics of irofulven combined with cisplatin in advanced solid tumor patients.

PATIENTS AND METHODS

Cisplatin and irofulven were given sequentially i.v. over 30 min on day 1 and 15 every 4 weeks. Four dose levels (DL) were explored: irofulven (mg/kg)/cisplatin (mg/m2): DL1: 0.3/30; DL2: 0.4/30; DL3: 0.4/40; DL4: 0.5/40. Dose-limiting toxicity (DLT) included dosing omission and delay > 1 week. MTD was the DL with DLT in 2/2 or > or = 2/6 patients during cycle 1-2.

RESULTS

Between March 2002 and April 2003, 33 patients were treated. DLT occurred in 1/6 patients in DL1 (hypomagnesemia, hypocalcemia); 1/6 in DL2 (thrombocytopenia); 2 heavily pretreated patients out of 6 patients in DL3 (neutropenic infection, thrombocytopenia, stomatitis); 2/3 in DL4 (asthenia, blurred vision). Three DLT occurred in 12 additional patients treated at DL2. No toxic deaths occurred; grade 4 toxicity and grade 3 non-hematological toxicity were infrequent. Six patients reported grade 1-2 visual events. Antitumor activity was observed over a broad spectrum of tumor types in all DLs: 1 partial response in bulky sarcoma (DL1); 1 clinical response in endometrial carcinoma (DL1); 2 partial responses not confirmed due to discontinuation (ovarian DL2, renal DL4); 8 stabilizations > 3 months; PSA response: 3/9 prostate cancer patients. Irofulven showed rapid elimination and high interpatient variability. Platinum and irofulven pharmacokinetics did not suggest drug-drug interactions.

CONCLUSION

Irofulven with cisplatin was adequately tolerated and substantial evidence of antitumor activity was observed. The recommended dose is irofulven 0.4 mg/kg and cisplatin 30 mg/m2.

A phase II study of irofulven in women with recurrent and heavily pretreated ovarian cancer

OBJECTIVE

To determine the safety and efficacy of a novel illudin S derivative, irofulven (MGI-114), in patients with recurrent ovarian cancer who had received extensive prior chemotherapy.

METHODS

The trial was an open label phase II study. Patients initially enrolled in this study were treated every 14 days with a dose of 24 mg/m2. Unexpected retinal toxicity associated with this dose and schedule lead to modification of the dosing to 0.55 mg/kg on the same schedule with a maximum individual dose of 50 mg. Dose reductions were permitted based on both hematologic and non-hematologic toxicities.

RESULTS

Seventy-four women were accrued and stratified into two cohorts including 58 women with platinum-resistant disease and 16 with platinum-sensitive disease. Non-hematologic toxicities included nausea, vomiting, and fatigue. Thirty-one women had between one and six visual symptoms, most were Grade 1 and 2 in nature. The majority of visual toxicities resolved either during treatment or post-treatment with irofulven. There was one partial response in each cohort with 19 (33%) and 8 (50%) of women having stable disease in the platinum-resistant and platinum-sensitive cohorts, respectively.

CONCLUSIONS

Irofulven at 24 mg/m2 on every 14-day schedule is associated with significant retinal toxicity in this patient population. Dosing at 0.55 mg/kg has persistent retinal toxicity, yet demonstrated only limited anti-tumor activity in a population of women who had received extensive prior chemotherapy.

Characterizations of irofulven cytotoxicity in combination with cisplatin and oxaliplatin in human colon, breast, and ovarian cancer cells

PURPOSE

This study assessed the cytotoxic effects of irofulven in combination with oxaliplatin and cisplatin in a panel of human cancer cell lines.

METHODS

Growth inhibition studies were performed using the human HT29 colon cancer cell line, irofulven-resistant derivative HT29/IF2, breast cancer cell line MCF7, and ovarian cancer line CAOV3. Irofulven-oxaliplatin combinations were compared with irofulven-cisplatin combinations in the same cell lines using similar experimental settings. Cells were exposed for 1 h to irofulven and then for 24 h to oxaliplatin or cisplatin and vice versa.

RESULTS

Single agent irofulven displayed cytotoxic effects against human colon HT29 cells, human breast cancer cell lines including MCF7, SKBR3, and ZR-75-1, and human ovarian cancer cell lines CAOV3, OVCAR3, and IGROV1, with OVCAR3 being the most sensitive cancer cell line (IC50: 2.4 microM). In all tested cell lines the oxaliplatin-irofulven combination led to clear evidence of synergistic activity. In HT29 and HT29/IF2, the sequence oxaliplatin followed by irofulven appears to be the most effective whereas in MCF7 cells, irofulven given prior to or simultaneously with oxaliplatin is more effective than the other schedule. The combination displays additive activity toward CAOV3 ovarian cells when irofulven was administered prior to or simultaneously with oxaliplatin and partially synergistic when oxaliplatin was followed by irofulven. In most of the cell lines, the sequence oxaliplatin followed by irofulven appears to be the most effective as compared to other schedules. A combination of irofulven with cisplatin has the same efficacy as with oxaliplatin for the same cell lines. Cell cycle studies show that irofulven increases the proportion of cells in the S phase. Cisplatin-irofulven and oxaliplatin-irofulven combinations block cells in G1/S and potently induce apoptosis.

CONCLUSION

Irofulven displays synergistic antiproliferative and pro-apoptotic effects when combined with oxaliplatin over a broad range of concentrations in human colon and breast cancer cells. Acquired resistance to irofulven has limited impact on the effects of cisplatin-irofulven and oxaliplatin-irofulven combinations. Based on these data, irofulven-oxaliplatin and cisplatin-irofulven combinations will be further explored in clinical trials, favoring the use schedules of oxaliplatin given prior to irofulven in patients with cancer.