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

Nucleotide excision repair deficiency is a targetable therapeutic vulnerability in clear cell renal cell carcinoma

Due to a demonstrated lack of DNA repair deficiencies, clear cell renal cell carcinoma (ccRCC) has not benefitted from targeted synthetic lethality-based therapies. We investigated whether nucleotide excision repair (NER) deficiency is present in an identifiable subset of ccRCC cases that would render those tumors sensitive to therapy targeting this specific DNA repair pathway aberration. We used functional assays that detect UV-induced 6-4 pyrimidine-pyrimidone photoproducts to quantify NER deficiency in ccRCC cell lines. We also measured sensitivity to irofulven, an experimental cancer therapeutic agent that specifically targets cells with inactivated transcription-coupled nucleotide excision repair (TC-NER). In order to detect NER deficiency in clinical biopsies, we assessed whole exome sequencing data for the presence of an NER deficiency associated mutational signature previously identified in ERCC2 mutant bladder cancer. Functional assays showed NER deficiency in ccRCC cells. Some cell lines showed irofulven sensitivity at a concentration that is well tolerated by patients. Prostaglandin reductase 1 (PTGR1), which activates irofulven, was also associated with this sensitivity. Next generation sequencing data of the cell lines showed NER deficiency-associated mutational signatures. A significant subset of ccRCC patients had the same signature and high PTGR1 expression. ccRCC cell line-based analysis showed that NER deficiency is likely present in this cancer type. Approximately 10% of ccRCC patients in the TCGA cohort showed mutational signatures consistent with ERCC2 inactivation associated NER deficiency and also substantial levels of PTGR1 expression. These patients may be responsive to irofulven, a previously abandoned anticancer agent that has minimal activity in NER-proficient cells.

Nucleotide excision repair deficiency is a targetable therapeutic vulnerability in clear cell renal cell carcinoma

Purpose

Due to a demonstrated lack of DNA repair deficiencies, clear cell renal cell carcinoma (ccRCC) has not benefitted from targeted synthetic lethality-based therapies. We investigated whether nucleotide excision repair (NER) deficiency is present in an identifiable subset of ccRCC cases that would render those tumors sensitive to therapy targeting this specific DNA repair pathway aberration.

Experimental Design

We used functional assays that detect UV-induced 6-4 pyrimidine-pyrimidone photoproducts to quantify NER deficiency in ccRCC cell lines. We also measured sensitivity to irofulven, an experimental cancer therapeutic agent that specifically targets cells with inactivated transcription-coupled nucleotide excision repair (TC-NER). In order to detect NER deficiency in clinical biopsies, we assessed whole exome sequencing data for the presence of an NER deficiency associated mutational signature previously identified in ERCC2 mutant bladder cancer.

Results

Functional assays showed NER deficiency in ccRCC cells. Irofulven sensitivity increased in some cell lines. Prostaglandin reductase 1 (PTGR1), which activates irofulven, was also associated with this sensitivity. Next generation sequencing data of the cell lines showed NER deficiency-associated mutational signatures. A significant subset of ccRCC patients had the same signature and high PTGR1 expression.

Conclusions

ccRCC cell line based analysis showed that NER deficiency is likely present in this cancer type. Approximately 10% of ccRCC patients in the TCGA cohort showed mutational signatures consistent with ERCC2 inactivation associated NER deficiency and also substantial levels of PTGR1 expression. These patients may be responsive to irofulven, a previously abandoned anticancer agent that has minimal activity in NER-proficient cells.

A Phase 1b trial of prexasertib in combination with chemoradiation in patients with locally advanced head and neck squamous cell carcinoma

BACKGROUND AND PURPOSE

This study explored the feasibility of safely combining prexasertib, with cisplatin-radiotherapy (Part A) or cetuximab-radiotherapy (Part B) in patients with previously untreated, locoregionally advanced head and neck squamous cell carcinoma (HNSCC).

MATERIALS AND METHODS

Escalating doses of prexasertib were administered in each combination using a modified Time-to-Event Continual Reassessment Method. Pharmacokinetic (PK) analysis was performed using standard non-compartmental methods of analysis. Antitumor activity was evaluated using RECIST version 1.1.

RESULTS

In Part A, 7 patients received 20 mg/m² prexasertib and cisplatin-radiotherapy. This dose exceeded the maximum tolerated dose (MTD); no other prexasertib dose was assessed. In Part B, 18 patients received prexasertib (20-40 mg/m²) and cetuximab-radiotherapy. The 30 mg/m² dose of prexasertib was determined as the MTD. Febrile neutropenia was the dose-limiting toxicity in each arm. Most common treatment-emergent adverse events with both combinations were neutropenia, thrombocytopenia, dysphagia, stomatitis, dry mouth, anemia, radiation skin injury [reported term radiation dermatitis], and nausea. PK of prexasertib was consistent with previously published data following prexasertib monotherapy. Overall response rate in Parts A and B was 71.4% and 83.3%, respectively. The small number of patients and follow-up limits the interpretation of efficacy data.

CONCLUSION

This study did not establish a safe dose of cisplatin-radiotherapy. However, it demonstrates the proof-of-principle that prexasertib could be safely combined with cetuximab-radiotherapy. These data will provide the basis to leverage the potential radio-sensitization properties of a CHK1 inhibitor in combination with radiation or other targeted agents in a variety of therapeutic settings.

Review on Pharmacology of Cisplatin: Clinical Use, Toxicity and Mechanism of Resistance of Cisplatin

Cisplatin is a chemotherapeutic drug that has been used in the treatment of various types of human cancers such as ovarian, lung, head and neck, testicular and bladder. Cisplatin has demonstrated efficacy against various types of cancers such as germ cell tumors, sarcomas, carcinomas as well as lymphomas. The current study presents a pharmacological review on the drug including its mechanism of action, resistance mechanism, and toxicity as well as its clinical applications. The mechanism of action of cisplatin has been associated with ability to crosslink with the urine bases on the DNA to form DNA adducts, preventing repair of the DNA leading to DNA damage and subsequently induces apoptosis within cancer cells. However, the drug exhibits certain level of resistance including increased repair of the damaged DNA, reduction in the accumulation of the drug intracellular and cytosolic inactivation of cisplatin. The drug is also characterized by various toxic side effects including nausea, nephrotoxicity, Cardiotoxicity, hepatotoxicity and neurotoxicity. Due various side effects as well as drug resistance, other anti-cancer drugs that contain platinum such as carboplatin and oxaliplatin among others have been used in combination with cisplatin in chemotherapeutic treatment of cancer. Strong evidence from research has demonstrated higher efficacy of combination of chemotherapies of cisplatin together with other drugs in overcoming drug resistance and in reducing toxic effects as well. Future studies that explore combinational techniques that target various mechanisms such as reduction in the uptake of cisplatin as well as inflammation could enhance efficacy of cisplatin.

Enantioselective total synthesis of (-)-acylfulvene and (-)-irofulven

We report our full account of the enantioselective total synthesis of (-)-acylfulvene (1) and (-)-irofulven (2), which features metathesis reactions for the rapid assembly of the molecular framework of these antitumor agents. We discuss (1) the application of an Evans Cu-catalyzed aldol addition reaction using a strained cyclopropyl ketenethioacetal, (2) an efficient enyne ring-closing metathesis cascade reaction in a challenging setting, (3) the reagent IPNBSH for a late-stage reductive allylic transposition reaction, and (4) the final RCM/dehydrogenation sequence for the formation of (-)-acylfulvene (1) and (-)-irofulven (2).

Synergy of Irofulven in combination with various anti-metabolites, enzyme inhibitors, and miscellaneous agents in MV522 lung carcinoma cells: marked interaction with gemcitabine and 5-fluorouracil

The novel agent Irofulven (HMAF, NSC 683863) has demonstrated significant antitumor activity against solid tumors in various xenograft models and human clinical trials. The antitumor potential of combining irofulven with 72 different anti-metabolite, enzyme inhibiting, and miscellaneous agents was investigated in this study. The human lung carcinoma MV522 cell line and its corresponding xenograft model were used to evaluate the activity of irofulven in combination with these different agents. Irofulven in combination with select anti-metabolites, notably cytidine or adenine-derived agents, displayed strong synergistic activity in both in vitro and in vivo studies. Agents demonstrating strong synergistic interaction with irofulven included gemcitabine, cyclocytidine, cytarabine, fludarabine phosphate, cladribine, and 5-fluorouracil. Other anti-metabolites, enzyme inhibitors, and a variety of miscellaneous agents failed to interact beneficially when administered in combination with irofulven. The therapeutic activity of irofulven is enhanced considerably when irofulven is combined with select anti-metabolite agents, and further clinical evaluation of these combinations is warranted. The synergistic interaction with these combinations may stem from a variety of actions including inhibition of the nucleotide excision repair (NER) pathway, topoisomerase I activity, and caspase-dependent and independent induction of apoptosis.

Quantitative correlation of drug bioactivation and deoxyadenosine alkylation by acylfulvene

Acylfulvenes (AFs) are a class of antitumor agents that exert their cytotoxic effects by forming covalent adducts with biomolecules, including DNA and proteins; clinical trials are ongoing for (-)-(hydroxymethyl)AF. Recently, depurinating DNA adducts N3-AF-deoxyadenosine (dAdo) and N7-AF-deoxyguanosine (dGuo) were identified from reactions of the parent compound, AF, with calf thymus DNA in the presence of the reductase enzyme alkenal/one oxidoreductase (AOR) and cofactor NADPH. We report here the development of a structure-specific quantitative analytical method for evaluating levels of the major base adduct N3-AF-adenine (Ade), which results from depurination of N3-AF-dAdo, and its utilization to further probe the relationship between AOR-mediated bioactivation and adduct formation in a cell-free system. As an internal standard, the isotopomer N3-AF-Ade-d3 was synthesized, and electrospray-ionization mass spectrometry coupled with high-performance liquid chromatography (HPLC-ESI-MS/MS) was used to detect and quantitate the adduct. This method was validated and found to be accurate (R2>or=0.99) and precise (relative standard deviation 5.8-6.4%), with a limit of detection of 2 fmol. DNA samples, to which the stable-isotope-labeled internal standard was added, were subjected to neutral thermal hydrolysis yielding N3-AF-Ade. Adducts were isolated by a simple solid-liquid methanol extraction procedure, and adduct formation was examined in the presence of either high (1-3 micromol) or low (15 nmol) levels of DNA. Absolute amounts of N3-AF-Ade were measured in cell-free reaction mixtures containing varying levels of AOR as the only drug-activating enzyme. The increase in adduct formation (5-100 adducts per 10(5) DNA bases) over a range of enzyme concentrations (1-24 nM of AOR) showed saturation type behavior. This study reports a sensitive HPLC-ESI-MS/MS method for quantitation of the major DNA adduct induced by AF and illustrates a correlation between N3-AF-Ade formation and AOR-mediated enzymatic activation in a cell-free system, thus providing a template for further studies of drug toxicity in cells and in vivo.

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.