Babaodan overcomes cisplatin resistance in cholangiocarcinoma via inhibiting YAP1

CONTEXT

Cholangiocarcinoma with highly heterogeneous, aggressive, and multidrug resistance has a poor prognosis. Although babaodan (BBD) combined with cisplatin improved non-small cell lung cancer efficacy, its impact on overcoming resistance in cholangiocarcinoma remains unexplored.

OBJECTIVE

This study explored the role and mechanism of BBD on cisplatin resistance in cholangiocarcinoma cells (CCAs).

MATERIALS AND METHODS

Cisplatin-resistant CCAs were exposed to varying concentrations of cisplatin (25-400 μg/mL) or BBD (0.25-1.00 mg/mL) for 48 h. IC50 values, inhibition ratios, apoptosis levels, DNA damage, glutathione (GSH) levels, oxidized forms of GSH, total GSH content, and glutaminase relative activity were evaluated using the cell counting kit 8, flow cytometry, comet assay, and relevant assay kits.

RESULTS

BBD-reduced the cisplatin IC50 in CCAs from 118.8 to 61.83 μg/mL, leading to increased inhibition rate, apoptosis, and DNA damage, and decreased expression of B-cell lymphoma-2, p-Yes-associated protein 1/Yes-associated protein 1, solute carrier family 1 member 5, activating transcription factor 4, and ERCC excision repair 1 in a dose-dependent manner with maximum reductions of 78.97%, 51.98%, 54.03%, 56.59%, and 63.22%, respectively; bcl2-associated X and gamma histone levels were increased by 0.43-115.77% and 22.15-53.39%. The impact of YAP1 knockdown on cisplatin-resistant CCAs resembled BBD. GSH, oxidized GSH species, total GSH content, and glutaminase activity in cisplatin-resistant CCAs with BBD treatment also decreased, while YAP1 overexpression countered BBD's effects.

DISCUSSION AND CONCLUSION

This study provides a scientific basis for BBD clinical application and provides a new direction for BBD biological mechanism research.

Targeting NFE2L2/KEAP1 Mutations in Advanced NSCLC With the TORC1/2 Inhibitor TAK-228

INTRODUCTION

Increased insight into the mutational landscape of squamous cell lung cancers (LUSCs) in the past decade has not translated into effective targeted therapies for patients with this disease. NRF2, encoded by NFE2L2, and its upstream regulator, KEAP1, control key aspects of redox balance and are frequently mutated in NSCLCs.

METHODS

Here, we describe the specific potent activity of TAK-228, a TORC1/2 inhibitor, in NSCLC models harboring NRF2-activating alterations and results of a phase 2 clinical trial of TAK-228 in patients with advanced NSCLC harboring NRF2-activating alterations including three cohorts (NFE2L2-mutated LUSC, KEAP1-mutated LUSC, KRAS/NFE2L2- or KEAP1-mutated NSCLC).

RESULTS

TAK-228 was most efficacious in a LUSC cohort with NFE2L2 alterations; the overall response rate was 25% and median progression-free survival was 8.9 months. Additional data suggest that concurrent inhibition of glutaminase with the glutaminase inhibitor CB-839 might overcome metabolic resistance to therapy in these patients.

CONCLUSIONS

TAK-228 has single-agent activity in patients with NRF2-activated LUSC. This study reframes oncogenic alterations as biologically relevant based on their downstream effects on metabolism. This trial represents, to the best of our knowledge, the first successful attempt at metabolically targeting NSCLC and identifies a promising targeted therapy for patients with LUSC, who are bereft of genotype-directed therapies.

In vivo characterization of glutamine metabolism identifies therapeutic targets in clear cell renal cell carcinoma

Targeting metabolic vulnerabilities has been proposed as a therapeutic strategy in renal cell carcinoma (RCC). Here, we analyzed the metabolism of patient-derived xenografts (tumorgrafts) from diverse subtypes of RCC. Tumorgrafts from VHL-mutant clear cell RCC (ccRCC) retained metabolic features of human ccRCC and engaged in oxidative and reductive glutamine metabolism. Genetic silencing of isocitrate dehydrogenase-1 or isocitrate dehydrogenase-2 impaired reductive labeling of tricarboxylic acid (TCA) cycle intermediates in vivo and suppressed growth of tumors generated from tumorgraft-derived cells. Glutaminase inhibition reduced the contribution of glutamine to the TCA cycle and resulted in modest suppression of tumorgraft growth. Infusions with [amide-15N]glutamine revealed persistent amidotransferase activity during glutaminase inhibition, and blocking these activities with the amidotransferase inhibitor JHU-083 also reduced tumor growth in both immunocompromised and immunocompetent mice. We conclude that ccRCC tumorgrafts catabolize glutamine via multiple pathways, perhaps explaining why it has been challenging to achieve therapeutic responses in patients by inhibiting glutaminase.

Efficacy and Safety of Telaglenastat Plus Cabozantinib vs Placebo Plus Cabozantinib in Patients With Advanced Renal Cell Carcinoma: The CANTATA Randomized Clinical Trial

Importance

Dysregulated metabolism is a hallmark of renal cell carcinoma (RCC). Glutaminase is a key enzyme that fuels tumor growth by converting glutamine to glutamate. Telaglenastat is an investigational, first-in-class, selective, oral glutaminase inhibitor that blocks glutamine utilization and downstream pathways. Preclinically, telaglenastat synergized with cabozantinib, a VEGFR2/MET/AXL inhibitor, in RCC models.

Objective

To compare the efficacy and safety of telaglenastat plus cabozantinib (Tela + Cabo) vs placebo plus cabozantinib (Pbo + Cabo).

Design, Setting, and Participants

CANTATA was a randomized, placebo-controlled, double-blind, pivotal trial conducted at sites in the US, Europe, Australia, and New Zealand. Eligible patients had metastatic clear-cell RCC following progression on 1 to 2 prior lines of therapy, including 1 or more antiangiogenic therapies or nivolumab plus ipilimumab. The data cutoff date was August 31, 2020. Data analysis was performed from December 2020 to February 2021.

Interventions

Patients were randomized 1:1 to receive oral cabozantinib (60 mg daily) with either telaglenastat (800 mg twice daily) or placebo until disease progression or unacceptable toxicity.

Main Outcomes and Measures

The primary end point was progression-free survival (Response Evaluation Criteria in Solid Tumors version 1.1) assessed by blinded independent radiology review.

Results

A total of 444 patients were randomized: 221 to Tela + Cabo (median [range] age, 61 [21-81] years; 47 [21%] women and 174 [79%] men) and 223 to Pbo + Cabo (median [range] age, 62 [29-83] years; 68 [30%] women and 155 [70%] men). A total of 276 (62%) patients had received prior immune checkpoint inhibitors, including 128 with prior nivolumab plus ipilimumab, 93 of whom had not received prior antiangiogenic therapy. Median progression-free survival was 9.2 months for Tela + Cabo vs 9.3 months for Pbo + Cabo (HR, 0.94; 95% CI, 0.74-1.21; P = .65). Overall response rates were 31% (69 of 221) with Tela + Cabo vs 28% (62 of 223) with Pbo + Cabo. Treatment-emergent adverse event (TEAE) rates were similar between arms. Grade 3 to 4 TEAEs occurred in 160 patients (71%) with Tela + Cabo and 172 patients (79%) with Pbo + Cabo and included hypertension (38 patients [17%] vs 40 patients [18%]) and diarrhea (34 patients [15%] vs 29 patients [13%]). Cabozantinib was discontinued due to AEs in 23 patients (10%) receiving Tela + Cabo and 33 patients (15%) receiving Pbo + Cabo.

Conclusions and Relevance

In this randomized clinical trial, telaglenastat did not improve the efficacy of cabozantinib in metastatic RCC. Tela + Cabo was well tolerated with AEs consistent with the known risks of both agents.

Trial Registration

ClinicalTrials.gov Identifier: NCT03428217.

Telaglenastat plus Everolimus in Advanced Renal Cell Carcinoma: A Randomized, Double-Blinded, Placebo-Controlled, Phase II ENTRATA Trial

PURPOSE

Glutaminase is a key enzyme, which supports elevated dependency of tumors on glutamine-dependent biosynthesis of metabolic intermediates. Dual targeting of glucose and glutamine metabolism by the mTOR inhibitor everolimus plus the oral glutaminase inhibitor telaglenastat showed preclinical synergistic anticancer effects, which translated to encouraging safety and efficacy findings in a phase I trial of 2L+ renal cell carcinoma (RCC). This study evaluated telaglenastat plus everolimus (TelaE) versus placebo plus everolimus (PboE) in patients with advanced/metastatic RCC (mRCC) in the 3L+ setting (NCT03163667).

PATIENTS AND METHODS

Eligible patients with mRCC, previously treated with at least two prior lines of therapy [including ≥1 VEGFR-targeted tyrosine kinase inhibitor (TKI)] were randomized 2:1 to receive E, plus Tela or Pbo, until disease progression or unacceptable toxicity. Primary endpoint was investigator-assessed progression-free survival (PFS; one-sided α <0.2).

RESULTS

Sixty-nine patients were randomized (46 TelaE, 23 PboE). Patients had a median three prior lines of therapy, including TKIs (100%) and checkpoint inhibitors (88%). At median follow-up of 7.5 months, median PFS was 3.8 months for TelaE versus 1.9 months for PboE [HR, 0.64; 95% confidence interval (CI), 0.34-1.20; one-sided P = 0.079]. One TelaE patient had a partial response and 26 had stable disease (SD). Eleven patients on PboE had SD. Treatment-emergent adverse events included fatigue, anemia, cough, dyspnea, elevated serum creatinine, and diarrhea; grade 3 to 4 events occurred in 74% TelaE patients versus 61% PboE.

CONCLUSIONS

TelaE was well tolerated and improved PFS versus PboE in patients with mRCC previously treated with TKIs and checkpoint inhibitors.

Tumoral microenvironment prevents de novo asparagine biosynthesis in B cell lymphoma, regardless of ASNS expression

Depletion of circulating asparagine with l-asparaginase (ASNase) is a mainstay of leukemia treatment and is under investigation in many cancers. Expression levels of asparagine synthetase (ASNS), which catalyzes asparagine synthesis, were considered predictive of cancer cell sensitivity to ASNase treatment, a notion recently challenged. Using [U-¹³C₅]-l-glutamine in vitro and in vivo in a mouse model of B cell lymphomas (BCLs), we demonstrated that supraphysiological or physiological concentrations of asparagine prevent de novo asparagine biosynthesis, regardless of ASNS expression levels. Overexpressing ASNS in ASNase-sensitive BCL was insufficient to confer resistance to ASNase treatment in vivo. Moreover, we showed that ASNase's glutaminase activity enables its maximal anticancer effect. Together, our results indicate that baseline ASNS expression (low or high) cannot dictate BCL dependence on de novo asparagine biosynthesis and predict BCL sensitivity to dual ASNase activity. Thus, except for ASNS-deficient cancer cells, ASNase's glutaminase activity should be considered in the clinic.

Marine Enzymes in Cancer: A New Paradigm

Over the last decades, the vast chemical and biodiversity of marine environment has been identified as an important source of new anticancer drugs. The evolution of marine life is a result of competition among microorganisms for space and nutrients in the marine environment, which drives marine microorganisms to generate diverse enzyme systems with unique properties to adapt to harsh conditions of ocean. Therefore, marine-derived sources offer novel enzymes endowed with extraordinary properties. Recent advances in cancer therapy have facilitated enzyme therapy as a promising tool. But, the available information on the use of enzymes derived from marine sources as therapeutic agents for cancer therapy is scanty. The potential utility of marine enzymes in cancer therapy will be discussed in this chapter.

Modulation of metastatic potential of B16F10 melanoma cells by acivicin: synergistic action of glutaminase and potentiation of cisplatin cytotoxicity

Treatment for metastatic melanoma has mostly been unsatisfactory despite advances in ongoing medical research. Here we investigated the role of acivicin, a glutamine analogue, singly and in combination with either E. coli glutaminase or cisplatin, on the growth, angiogenic activity and invasiveness of B16F10 cells in vitro and after allografting in C57BL/6 mice. B16F10 melanoma colonization in the lungs of mice was measured by monitoring colony counts. Host toxicity was assessed with reference to tumor bearing host's weight and survivability. Acivicin promoted melanoma dormancy and reduced melanoma associated angiogenic factors like VEGF level and vessel diameter. Acivicin in combination with glutaminase significantly suppressed tumor growth by 66.7% and increased life-span by 43.5% without host toxicity. Tumor VEGF content was significantly lowered by combination therapy as assessed by ELISA. Accelerated cytotoxicity, reduced invasion and enhanced apoptosis of melanoma cells were exhibited in vitro by combined than by single agent treatment. Moreover, invasion of melanoma cells through matrigel chambers was reduced in presence of acivicin and glutaminase combination. These findings support future studies of acivicin in combination with other anticancer agents for prevention of melanoma metastasis.

Effect of purified glutaminase from human ascites fluid on experimental tumor bearing mice

Glutamine is the major respiratory fuel and energy source of the rapidly proliferating tumor cells and that is why glutamine clearance by glutaminase therapy provides an opportunity to fight against the neoplasm. Glutaminase from bacterial source was tried on experimental models but had to be excluded because of its limited efficacy. Search for a better glutaminase continued exploiting the mammalian sources. In the present study, glutaminase purified from human ovarian cancer ascites fluid was used in experimental solid and ascites mice model alone and in combination with Cu-Sulphate and heparin. Cumulative findings indicate that the enzyme alone is quite effective in lowering tumor burden and reducing not only the tumor induced angiogenesis, but also an angiogenic inducer, heparin mediated angiogenesis. However, the presence of Cu with the enzyme, amplified the antineoplastic response by improving anti-angiogenic potential and hematological status of the tumor bearing host. Therefore, Cu-glutaminase combination strengthened the hypothesis that together they may provide a better therapeutic regimen in experimental mice tumor model.

A phase I and pharmacodynamic evaluation of polyethylene glycol-conjugated L-asparaginase in patients with advanced solid tumors

PURPOSE

To evaluate the in vitro activity of polyethylene glycol-conjugated L-asparaginase (PEG-Lasparaginase) against fresh human tumor specimens, using the human tumor clonogenic assay (HTCA), and to perform a phase I dose-escalation clinical trial of PEG-L-asparaginase. The goal of the clinical study was to determine the toxicity and optimum biologic dose of PEG-L-asparaginase based on depletion of serum L-asparagine in patients with advanced solid tumors.

METHODS

A modified method for determination of serum L-asparagine is described. PEG-L-asparaginase was administered by intramuscular injection every 2 weeks to 28 patients with various types of advanced solid tumor malignancies. At least 3 patients were evaluated at each dose level: 250 IU/m2, 500 IU/m2, 1,000 IU/m2, 1,500 IU/m2, 2,000 IU/m2.

RESULTS

The in vitro HTCA studies suggested good antitumor activity against malignant melanoma and multiple myeloma. Serum L-asparagine was most consistently and profoundly depleted (up to 4 weeks) in patients treated with 2,000 IU/m2. Patients receiving this dose level also showed more frequent grade 1, grade 2, and occasional grade 3 toxicities of fatigue/weakness, nausea/vomiting, and anorexia/ weight loss. Three patients developed hypersensitivity reactions, but these were not dose related. Two patients developed deep vein thromboses. We saw no episodes of clinical pancreatitis, but there were minor fluctuations of serum amylase and lipase. We saw no partial or complete responses in patients treated in this study, including 11 patients with malignant melanoma.

CONCLUSIONS

We conclude that PEG-L-asparaginase is generally well tolerated in patients with advanced solid tumors, and a dosage of 2,000 IU/m2 by intramuscular injection every 2 weeks results in significant depletion of serum L-asparagine.

A general survey of glutamine level in different tissues of murine solid tumor bearing mice before and after therapy with purified glutaminase

Distribution of glutamine level in different tissues of tumor bearing mice such as brain, liver, kidney, spleen, large and small intestine and the tumor itself were studied in three solid tumor models, viz, Ehrlich ascites carcinoma, Sarcoma-180 and methylcholanthrene induced carcinoma. Tumor bearing mice were subjected to therapy for 7 days with the glutaminase purified from malignant S-180 cell. The results exhibit a significant decrease in tumor burden after enzyme therapy. Host tissue glutamine levels were significantly elevated in tumor bearing untreated mice in comparison to the normal ones, while significant lower values were obtained after enzyme therapy. It therefore appears that elevated levels of glutamine in host tissue are associated with the tumor burden.

Angiogenesis a putative new approach in glutamine related therapy

Angiogenesis or the generation of new blood vessels, is an important factor regarding the growth of a tumor. Hence, it becomes a necessary parameter of any kind in therapeutic studies. Glutamine is an essential nutrient of tumor tissue and glutamine related therapy involves clearance of circulatory glutamine by glutaminase. So, whether this enzyme has any effect on angiogenesis of a tumor or not becomes an obvious question. To address this question, this study has been carried out with different murine tumor models. The results indicate that purified glutaminase reduces tumor volume as well as restricts the generation of new blood vessels. Glutaminase is effective in the case of solid as well as ascites tumor models. In the case of induced cancer, the host exhibits delayed onset of neoplasia following enzyme treatment and tumor host interactions determine the intensity of the neovascularisation process. Therefore, it can be concluded that this enzyme might be an effective agent against cancer metastasis.

Neovascularisation offers a new perspective to glutamine related therapy

Angiogenesis or the generation of new blood vessel, is an important factor in the growth of a solid tumor. Hence, it becomes a necessary parameter of any kind of therapeutic study. Glutamine is an essential nutrient of tumor tissue and glutamine related therapy involves clearance of circulatory glutamine by glutaminase. Therefore, using different murine solid tumor models, the present study was undertaken to find out whether the S-180 cell glutaminase has any effect on angiogenesis of solid tumor, or not. Result indicates that the purified S-180 cell glutaminase reduces tumor volume and restrict the generation of neo blood vessels. Therefore, it can be concluded that this enzyme may be an effective device against the cancer metastasis.

Isolation and purification of phosphate dependent glutaminase from sarcoma-180 tumor and its antineoplastic effects on murine model system

High rate of glutamine use is a characteristic of tumor cell both in vivo and in vitro and experimental cancer therapies have developed by depriving tumor cells of glutamine. In several investigations, bacterial glutaminase was found to be a potent therapeutic agent against varieties of tumor, but it showed suppressive effects on haematopoietic systems and inhibitory effects on normal lymphocytic blastogenesis. No antineoplastic study has nevertheless been undertaken with glutaminase enzyme purified from mammalian source. In the present study we report the purification of glutaminase enzyme from mitochondria of highly malignant S-180 cell using ion exchange chromatography and affinity column chromatography of glutamine. Purified enzyme is a kidney type phosphate dependent glutaminase with Mr 64 KD. Effect of enzyme therapy has been investigated in transplantable as well as induced tumor model in both ascites and solid form. It has been observed that the enzyme at the total dose of 10 unit/mouse successfully inhibited the tumor burden both in ascitic and solid tumor and subsequently increases the host's life span. There was no significant toxic effect on the peripheral blood cells.

Investigation on glutamine amidohydrolase (EC 3.5.1.2) and glutamine aminotransferase (EC 2.5.1.15) activity in liver and plasma of EAC-bearing mice following glutaminase therapy

The anti-neoplastic activity of bacterial glutaminase on Ehrlich ascites tumor-bearing mice was studied by determining the reduction in the tumor cell count and extension of life span of the host after therapy. The therapeutic effect of glutaminase in relation to change in activity of glutaminolytic enzymes (glutamine amidohydrolase (GNase) and glutamine aminotransferase (GAt)) in liver and plasma were also studied. Bacterial glutaminase was shown to be effective in lowering the tumor burden with increased life span of the host. Glutamine amidohydrolase activity in the liver and plasma was raised significantly with increased tumor burden, whereas GAt activity remained unchanged. Following glutaminase therapy, this high level of GNase activity decreased in comparison to the untreated control. These changes were not seen when normal mice were treated with the same enzyme. Thus alteration in the enzyme levels, particularly GNase was observed to have some correlation with progression of the tumor growth.

[13N]Ammonia and L-[amide-13N]glutamine metabolism in glutaminase-sensitive and glutaminase-resistant murine tumors

The short-term metabolic fate of labeled nitrogen derived from [13N]ammonia or from L-[amide-13N]glutamine was determined in murine tumors known to be resistant (Ridgeway Osteogenic Sarcoma (ROS] or sensitive (Sarcoma-180 (S-180)) to glutaminase therapy. At 5 min after intraperitoneal injection of [13N]ammonia or of L-[amide-13N]glutamine, only about 0.7% of the label recovered in both tumors was in protein and nucleic acid. After [13N]ammonia administration, most of the label (over 80%) was in a metabolized form; a large portion of this metabolized label (50-57%) was in the urea fraction with a smaller amount in glutamine (37-42%). The major short-term fate of label derived from L-[amide-13N]glutamine was incorporation into components of the urea cycle with smaller amounts in the acidic metabolites and in acidic amino acids. No labeled urea was found during in vitro studies in which S-180 tumor slices were incubated with [13N]ammonia, suggesting that the [13N]urea formed in the tumor in the in vivo experiments was not due to de novo synthesis through carbamyl phosphate in the tumor. Both tumors exhibited very low glutamine synthetase activity. Following glutaminase treatment, glutamine synthetase and gamma-glutamyltransferase activities, while remaining low, increased in the resistant tumor but not in the sensitive tumor; this increase may be related to the insensitivity of the ROS tumor toward glutaminase treatment.

Sensitivity of cultured pancreatic carcinoma cells to Acinetobacter glutaminase-asparaginase

Cultured human pancreatic carcinoma cells (MIA PaCa-2) have been shown previously to be very sensitive to E. coli L-asparaginase (EC II). The present studies have demonstrated that another enzyme, Acinetobacter glutaminase-asparaginase (AGA) is much more effective in inhibiting cell growth. At the concentration of 0.0025 U/ml of AGA activity the enzyme totally inhibited cell growth, whereas the EC II with the same concentration did not show any effect. The inhibition of cell growth correlated well with inhibition of protein and glycoprotein synthesis. The addition of L-glutamine at the concentration of 1 mM completely reversed the inhibition of protein synthesis. Similarly, the addition of L-glutamine at the concentration of 3 mM daily on 3 successive days after adding AGA resulted in significant reversal of growth inhibition. The results of this study indicate that the action of AGA on MIA PaCa-2 is, to a great extent, exerted through its L-glutaminase activity.

Clinical evaluation of succinylated Acinetobacter glutaminase-asparaginase in adult leukemia

We treated 13 adult patients with acute leukemia or chronic myelocytic leukemia (CML) in blast phase using succinylated Acinetobacter glutaminase-asparaginase (SAGA) administered on a daily dose schedule. SAGA reduced the peripheral blast count in two patients with acute lymphoblastic leukemia and two with blastic CML; however, no patient achieved either complete or partial remission. Marked central nervous system toxic effects (encephalopathy and coma) were observed, limiting treatment in patients whose disease appeared responsive; this effect finally prompted early discontinuance of the trial. Other toxic effects observed included nausea, hyperglycemia, and respiratory alkalosis. Hypersensitivity reactions to the enzyme were not seen. Pharmacologic analyses showed that prolonged blood glutamine depletion was achieved only by daily enzyme administration; however, we noted the importance of performing amino acid analysis on blood which was deproteinized immediately following phlebotomy. Our results demonstrate excessive central nervous system toxicity when glutaminase-asparaginase is administered on a daily schedule. Because of this effect, we propose that future trials of similar enzymes be limited to short courses of enzyme therapy, possibly with the addition of antimetabolites or amino acid analogs, which could enhance the antitumor effect without increasing toxicity.

Amino acid utilization and urine protein excretion in children treated with succinylated Acinetobacter glutaminase-asparaginase

Amino acid utilization was evaluated in seven children with acute lymphocytic leukemia treated with succinylated Acinetobacter glutaminase-asparaginase. All patients received food p.o. ad libitum and glucose-electrolyte solutions i.v.; four patients received an i.v. amino acid supplement (1.5 g/kg/day). Although all patients were in negative energy balance, there was a significant linear regression between nitrogen balance and nitrogen intake during Days 1 to 7 and Days 8 to 14 of the study. The slope of the regression line, reflecting exogenous nitrogen utilization, was not significantly different from that found in healthy young men ingesting adequate or subadequate energy intakes. The Y-intercept (-210 mg/kg/day) indicated an obligatory nitrogen loss that was much greater than normal. Most of the nitrogen loss was due to urinary excretion. Ammonia and urea accounted for 77 to 91% of the urine nitrogen. Urinary glutamate accounted for 4 to 10% of this loss. Urine protein excretion was abnormally high in each of the patients, ranging from 987 to 3440 mg/day. Urine excretion of N-acetyl-beta-glucosaminidase and beta 2-microglobulin was also abnormally high, despite normal blood urea nitrogen and serum creatinine, suggesting that these children had renal tubular dysfunction. The antileukemic effect of succinylated Acinetobacter glutaminase-asparaginase did not appear to be altered by amino acid supplementation. These data indicate that amino acid supplementation can improve nutritional status in patients treated with succinylated Acinetobacter glutaminase-asparaginase.

Phase I evaluation of succinylated Acinetobacter glutaminase-asparaginase in adults

Succinylated Acinetobacter glutaminase-asparaginase (SAGA) has broader antitumor activity than Escherichia coli L-asparaginase in experimental systems; moreover, drug resistance does not develop in tumor cell lines initially sensitive to this enzyme. We have investigated the pharmacology and toxicology of SAGA after both single-dose and serial daily dose injections in 20 adult patients. Glutaminase activity in plasma after i.v. injection of single doses did not follow simple first-order kinetics (half-life during the initial 24 hr was 21 +/- 9 hr. A linear relation was observed between increasing doses of SAGA and resultant levels of plasma enzyme activity and blood glutamate. Assay of whole blood which had been deproteinized immediately following phlebotomy showed that single doses of SAGA lowered glutamine only transiently to nondetectable levels; serial daily doses were required to achieve and maintain continuous glutamine depletion. Reversible depression of the central nervous system, ranging from encephalopathy to coma, occurred in a dose-related manner and was dose limiting. Other prominent reactions included respiratory alkalosis, hyperglycemia, nausea, and vomiting. Transient antitumor effects were noted in two patients with solid tumors and in two patients with leukemia. SAGA causes considerable neurotoxicity in adults which requires close patient monitoring. Phase II studies in leukemic patients are in progress.

Enhancement of melphalan therapy with glutaminase:asparaginase

Depletion of glutamine with Acinetobacter glutaminase:asparaginase promotes melphalan uptake by and cytotoxicity to murine L1210 cells in vitro. Combined treatment of tumor bearing mice with these two agents increases the therapeutic response.

Amino acid degrading enzymes for cancer therapy

The development of microbial enzymes for cancer therapy presents difficulties not commonly experienced with biological drugs. The development of the enzyme asparaginase from Escherichia coli in the USA and of the serologically different asparaginase from the plant pathogen Erwinia carotovora in this Establishment, has not only added to the choice of antileukaemia drugs but also provided a valuable guide to the selection and development of new therapeutic enzymes. Our own programme has led to the study of enzymes that degrade other amino acids (glutamine, arginine, phenylalanine and tyrosine) that appear to be important to certain leukaemia cells. Microbes with only remote associations with man were considered as a source of these to minimize initial immunological sensitivity. In the case of erwinia asparaginase the benefits of this have probably included a lower incidence of anaphylaxis compared with the escherichia enzyme. The selection of a stable, high-affinity enzyme that operates efficiently under physiological conditions ensures effective depletion of a circulating amino acid but the choice is very limited. It is also difficult to assess from laboratory tests the likely persistence, toxicity and efficacy of the enzyme in clinical use and to arrive at meaningful biological tests for the quality control of the finished product. Some of the difficulties will be described and proposals made for criteria of acceptance for this type of drug in experimental use.

Purification and properties of L-glutaminase-L-asparaginase from Pseudomonas acidovorans

An enzyme that catalyzes the hydrolysis of both glutamine and asparagine has been purified to homogeneity from extracts of Pseudomonas acidovorans. The enzyme having a ratio of glutaminase to asparaginase of 1.45:1.0 can be purified by a relatively simple procedure and is stable upon storage. The glutaminase-asparaginase has a relatively high affinity for L-asparagine (Km=1.5 X 10(-5) M) and L-glutamine (Km=2.2 X 10(-5) M) and has a molecular weight of approximately 156,000 the subunit molecular weight being approximately 39,000. Injections of the enzyme produced only slight increases in the survival time of C3H/HE mice carrying the asparagine-requiring 6C2HED Gardner lymphoma and of white Swiss mice carrying the glutamine-requiring Ehrlich lymphoma.

Chronic lymphocytic leukemia: correlation of clinical course and therapeutic response with in vitro testing and morphology of lymphocytes

Forty-two patients with chronic lymphocytic leukemia (CLL) were studied for morphology of lymphocytes by light and electron microscopy (EM), in vitro responses of lymphocytes to a battery of physical and chemical agents, overall clinical status, immunologic status, course, and response to therapy. CLL lymphocytes could be classified by EM into four groups on the basis of cell size and nuclear contour and by light microscopy into two groups, small cells and large cells (lymphosarcoma cells). Patient survival did not vary with cell size or morphology as determined by light or electron microscopy. In vitro testing of CLL lymphocytes following exposure to X-ray, PHA, DMSO 2 hr at 43 degrees C, prednisolone, glutaminase, and asparaginase permitted a separation of patients into categories of normal and abnormal in vitro responses. A normal in vitro response predicted a good response to therapy but an abnormal in vitro response did not preclude a good response to therapy. Following therapy, normalization of abnormal EM morphology and in vitro response was seen in some patients. Most patients tested had decreased serum immunoglobulins and abnormal PHA responses. There was a high incidence of infections and second neoplasms. Immunologic deficits could not be correlated with variations in lymphocyte morphology or in vitro response.

Physical properties of antitumor glutaminase-asparaginase from Pseudomonas 7A

Glutaminase-asparaginase from Pseudomonas 7A appears to have four subunits with a molecular weight of 36,000 +/- 500 by sedimentation equilibrium in 5.9 M guanidine HCl and 34,000 by amino acid analysis. Analytic sedimentation equilibrium of the native enzyme showed a molecular weight of 140,000 +/- 3,300 with no signs of association or dissociation. Moving boundary and zone sedimentation in buffer showed normal behavior with sedimentation coefficients of 7.92 and 7.75 S, respectively. In contrast, the enzyme appeared to polymerize during zone sedimentation when the initial protein concentration was greater than 1 mg/ml and the buffer contained asparagine, glutamine, or 5-diazo-4-oxonorvaline. An extension of our method for active enzyme sedimentation is described which utilizes the changes in absorption during hydrolysis of asparagine by low concentrations of enzyme. Polymerization was not seen under these conditions.

Bacterial glutaminase in treatment of acute leukaemia

A glutaminase-asparaginase enzyme from Achromobacter sp has antitumour activity in vitro and in animals. Glutaminase was administered in doses of 3500-20 000 IU/m2 body surface area/day to six patients with acute lymphoblastic leukaemia (ALL) and three patients with acute myeloid leukaemia (AML). The enzyme had a blood half life of 80 minutes but depletion of blood glutamine persisted for 12 hours after single doses. Seven patients, including four (two with AML and two with ALL) resistant to asparaginase, received repeated doses of glutaminase. Antileukaemic effects were observed in all seven; one elderly patient developed metabolic acidosis. Study of this new antileukaemic agent in patients with acute leukaemia at an earlier stage of their disease is now justified.