Trimetrexate for the treatment of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome

Low Lymphocyte Proportion in Bronchoalveolar Lavage Fluid as a Risk Factor Associated with the Change from Trimethoprim/sulfamethoxazole used as First-Line Treatment for Pneumocystis jirovecii Pneumonia

Background

Trimethoprim/sufamethoxazole (TMP/SMX) is the recommended treatment for Pneumocystis jirovecii pneumonia (PCP). However, the efficacy and the safety of alternative salvage treatments are less guarauteed especially when patient experiences treatment failure and/or an adverse drug reactions (ADR). The purpose of this study is to recognize potential risk factors imitating successful treatment with TMP/SMX among PCP patients.

Materials and Methods

Ninety one adult patients diagnosed with PCP were included after searching electronical medical records from January 2013 through July 2015 at Asan Medical Center Seoul, Korea. We compared clinical characteristics and laboratory findings including bronchoalveolar lavage (BAL) fluid analysis in patients who experienced TMP/SMX treatment failure or ADR (the case group) versus those who did not (the control group).

Results

Among the enrolled PCP patients, 39 (42.9%) required salvage treatment owing to either treatment failure (28, 28.6%) and/or ADR (17, 18.7%). The BAL lymphocyte percentage (25% [IQR, 8–40%] vs. 47% [IQR, 15–62%]; P = 0.005) was lower in the case group. Diabetes mellitus (adjusted odds ratio [aOR] 4.98, 95% confidence interval [95% CI] 1.20–18.58), glomerular filtration rate ≤50 mL/min (aOR 4.48, 95% CI 1.08–18.66), and BAL lymphocyte percentage ≤45% (aOR 9.25, 95% CI 2.47–34.58) were independently associated with the case group in multivariate analysis.

Conclusion

This study suggests that BAL lymphocyte count may play some role during PCP treatment. Further studies should be followed to reveal what the role of BAL lymphocyte is in the PCP treatment.

Treatment of Pneumocystis jirovecii pneumonia in HIV-infected patients: a review

INTRODUCTION

Pneumocystis pneumonia is a potentially life-threatening pulmonary infection that occurs in immunocompromised individuals and HIV-infected patients with a low CD4 cell count. Trimethoprim-sulfamethoxazole has been used as the first-line agent for treatment, but mutations within dihydropteroate synthase gene render potential resistance to sulfamide. Despite advances of combination antiretroviral therapy (cART), Pneumocystis pneumonia continues to occur in HIV-infected patients with late presentation for cART or virological and immunological failure after receiving cART. Areas covered: This review summarizes the diagnosis and first-line and alternative treatment and prophylaxis for Pneumocystis pneumonia in HIV-infected patients. Articles for this review were identified through searching PubMed. Search terms included: 'Pneumocystis pneumonia', 'Pneumocystis jirovecii pneumonia', 'Pneumocystis carinii pneumonia', 'trimethoprim-sulfamethoxazole', 'primaquine', 'trimetrexate', 'dapsone', 'pentamidine', 'atovaquone', 'echinocandins', 'human immunodeficiency virus infection', 'acquired immunodeficiency syndrome', 'resistance to sulfamide' and combinations of these terms. We limited the search to English language papers that were published between 1981 and March 2017. We screened all identified articles and cross-referenced studies from retrieved articles. Expert commentary: Trimethoprim-sulfamethoxazole will continue to be the first-line agent for Pneumocystis pneumonia given its cost, availability of both oral and parenteral formulations, and effectiveness or efficacy in both treatment and prophylaxis. Whether resistance due to mutations within dihydropteroate synthase gene compromises treatment effectiveness remains controversial. Continued search for effective alternatives with better safety profiles for Pneumocystis pneumonia is warranted.

Folate During Antifolate Chemotherapy: What We Know... and Do Not Know

The nutrient folate is essential for normal cell growth and development. Enzymes that require folate as a cofactor have been common targets for chemotherapeutic agents. Limited clinical guidance is available regarding optimal levels of dietary or supplemental folate intake during antifolate chemotherapy to meet the goals of minimizing treatment-related toxicity yet preserving treatment effectiveness. Patients with higher folate intake may experience less treatment-related toxicities; however, the concern is that folate may interfere with the effectiveness of the antifolate treatment and possibly support tumor growth. This article will review folate and antifolate metabolism and review the current body of knowledge regarding the interactions between folates and antifolates. Future research in this area should include evaluation of pretreatment folate status and dietary and supplemental folate intake before, during, and after treatment.

Co-infection of Mycobacterium tuberculosis and Pneumocystis jirovecii in the Iranian Patients With Human Immunodeficiency Virus

Background:

Based on the authors’ knowledge, there is no study on the co-infection of opportunistic agents such as Mycobacterium tuberculosis and Pneumocystis jirovecii in the lungs of Iranian patients with immunosuppression.

Objectives:

The current study aimed to show the rate of co-infection of M. tuberculosis and P. jirovecii in patients with Human Immunodeficiency Virus (HIV).

Patients and Methods:

Forty-five pulmonary samples were collected from 30 patients with HIV who also infected with Tuberculosis and Pneumonia. All of the patients were admitted to two university hospitals of Mycobacteriology and the Iranian HIV/AIDS research centers. DNA of P. jirovecii was detected using nested-Polymerase Chain Reaction (nested-PCR) assay.

Results:

All of the patients were male with the mean age of 32.95 ± 7.15 years. The mean of CD4 cell count was 109.25 cell/mm³. Of 30 patients with HIV, three (10%) were co-infected with M. tuberculosis and P. jirovecii. No other causes of pneumonia were found in those three patients and CD4 cell counts less than 50 cell/mm³ was reported.

Conclusions:

The results of the current study showed a high rate of co-infection of M. tuberculosis and P. jirovecii in the Iranian patients with HIV. As the immune system condition worsened, the probability of occurrence of Pneumocystis Pneumonia (PCP) increased. Therefore, more specific, most rapid and sensitive tests should be utilized for diagnosis of PCP in this group of patients.

Trimetrexate and folinic acid: a valuable salvage option for Pneumocystis jirovecii pneumonia

The best management strategy for HIV patients who fail to respond to first-line therapy for Pneumocystis jirovecii pneumonia is currently unclear. We identified all patients who were treated with trimetrexate and folinic acid who failed 7 or more days of cotrimoxazole, clindamycin-primaquine or dapsone-trimethoprim between 1996 and 2006. Trimetrexate was tolerated in 100% of cases with no treatment termination secondary to adverse drug reactions. Despite severe disease, 71% of patients were alive after 12 weeks.

Towards new antifolates targeting eukaryotic opportunistic infections

Trimethoprim, an antifolate commonly prescribed in combination with sulfamethoxazole, potently inhibits several prokaryotic species of dihydrofolate reductase (DHFR). However, several eukaryotic pathogenic organisms are resistant to trimethoprim, preventing its effective use as a therapeutic for those infections. We have been building a program to reengineer trimethoprim to more potently and selectively inhibit eukaryotic species of DHFR as a viable strategy for new drug discovery targeting several opportunistic pathogens. We have developed a series of compounds that exhibit potent and selective inhibition of DHFR from the parasitic protozoa Cryptosporidium and Toxoplasma as well as the fungus Candida glabrata. A comparison of the structures of DHFR from the fungal species Candida glabrata and Pneumocystis suggests that the compounds may also potently inhibit Pneumocystis DHFR.

N9-substituted 2,4-diaminoquinazolines: synthesis and biological evaluation of lipophilic inhibitors of pneumocystis carinii and toxoplasma gondii dihydrofolate reductase

N9-substituted 2,4-diaminoquinazolines were synthesized and evaluated as inhibitors of Pneumocystis carinii (pc) and Toxoplasma gondii (tg) dihydrofolate reductase (DHFR). Reduction of commercially available 2,4-diamino-6-nitroquinazoline 14 with Raney nickel afforded 2,4,6-triaminoquinazoline 15. Reductive amination of 15 with the appropriate benzaldehydes or naphthaldehydes, followed by N9-alkylation, afforded the target compounds 5- 13. In the 2,5-dimethoxybenzylamino substituted quinazoline analogues, replacement of the N9-CH 3 group of 4 with the N9-C2H5 group of 8 resulted in a 9- and 8-fold increase in potency against pcDHFR and tgDHFR, respectively. The N9-C2H5 substituted compound 8 was highly potent, with IC50 values of 9.9 and 3.7 nM against pcDHFR and tgDHFR, respectively. N9-propyl and N9-cyclopropyl methyl substitutions did not afford further increases in potency. This study indicates that the N9-ethyl substitution is optimum for inhibitory activity against pcDHFR and tgDHFR for the 2,4-diaminoquinazolines. Selectivity was unaffected by N9 substitution.

Synthesis, dihydrofolate reductase inhibition, antitumor testing, and molecular modeling study of some new 4(3H)-quinazolinone analogs

In order to produce potent new leads for anticancer drugs, a new series of quinazoline analogs was designed to resemble methotrexate (MTX, 1) structure features and fitted with functional groups believed to enhance inhibition of mammalian DHFR activity. Molecular modeling studies were used to assess the fit of these compounds within the active site of human DHFR. The synthesized compounds were evaluated for their ability to inhibit mammalian DHFR in vitro and for their antitumor activity in a standard in vitro tissue culture assay panel. Compounds 28, 30, and 31 were the most active DHFR inhibitors with IC(50) values of 0.5, 0.4, and 0.4microM, respectively. The most active antitumor agents in this study were compounds 19, 31, 41, and 47 with median growth inhibitory concentrations (GI(50)) of 20.1, 23.5, 26.7, and 9.1microM, respectively. Of this series of compounds, only compound 31 combined antitumor potency with potent DHFR inhibition; the other active antitumor compounds (19, 41, and 47) all had DHFR IC(50) values above 15microM, suggesting that they might exert their antitumor potency through some other mode of action. Alternatively, the compounds could differ significantly in uptake or concentration within mammalian cells.

Etiology of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a serious lower respiratory tract infection associated with significant morbidity and mortality that is characterized by disputes over diagnostic evaluations and therapeutic decisions. With the widespread use of broad-spectrum antimicrobial agents and the increasing number of immunocompromised hosts, the etiology and the drug resistance patterns of pathogens responsible for CAP have changed. Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis remain the leading causes of CAP in immunocompetent patients. Opportunistic infections with organisms such as Pneumocystis jiroveci and Mycobacterium tuberculosis and other opportunistic fungal pneumonias should also be considered in the differential diagnosis of CAP in immunocompromised patients. This article examines the current peer-reviewed literature on etiology, risk factors, and outcomes of patients with CAP.

Preliminary in vitro studies on two potent, water-soluble trimethoprim analogues with exceptional species selectivity against dihydrofolate reductase from Pneumocystis carinii and Mycobacterium avium

2,4-Diamino-5-[3',4'-dimethoxy-5'-(5-carboxy-1-pentynyl)]benzylpyrimidine (6) and 2,4-diamino-5-[3',4'-dimethoxy-5'-(4-carboxyphenylethynyl)benzylpyrimidine (7) were synthesized from 2,4-diamino-5-(5'-iodo-3',4'-dimethoxybenzyl)pyrimidine (9) via a Sonogashira reaction with appropriate acetylenic esters followed by saponification, and were tested as inhibitors of dihydrofolate reductase (DHFR) from Pneumocystis carinii (Pc), Toxoplasma gondii (Tg), Mycobacterium avium (Ma), and rat in comparison with the widely used antibacterial agent 2,4-diamino-5-(3',4',5'-trimethoxybenzyl)pyrimidine (trimethoprim, TMP). The selectivity index (SI) for each compound was calculated by dividing its 50% inhibitory concentration (IC(50)) against rat DHFR by its IC(50) against Pc, Tg, or Ma DHFR. The IC(50) of 6 against Pc DHFR was 1.0 nM, with an SI of 5000. Compound 7 had an IC(50) of 8.2 nM against Ma DHFR, with an SI of 11000. By comparison, the IC(50) of TMP was 12000 nM against Pc, 300 nM against Ma, and 180000 against rat DHFR. The potency and selectivity values of 6 and 7 were not as high against Tg as they were against Pc or Ma DHFR, but nonetheless exceeded those of TMP. Because of the outstanding selectivity of 6 against Pc and of 7 against Ma DHFR, these novel analogues may be viewed as promising leads for further structure-activity optimization.

Design, synthesis, and computational affinity prediction of ester soft drugs as inhibitors of dihydrofolate reductase from Pneumocystis carinii

A series of dihydrofolate reductase (DHFR) inhibitors, where the methylenamino-bridge of non-classical inhibitors was replaced with an ester function, have been prepared as potential soft drugs intended for inhalation against Pneumocystis carinii pneumonia (PCP). Several of the new ester-based inhibitors that should serve as good substrates for the ubiquitous esterases and possibly constitute safer alternatives to metabolically stable DHFR inhibitors administered orally, were found to be potent inhibitors of P. carinii DHFR (pcDHFR). Although the objectives of the present program is to achieve a favorable toxicity profile by applying the soft drug concept, a high preference for inhibition of the fungal DHFR versus the mammalian DHFR is still desirable to suppress host toxicity at the site of administration. Compounds with a slight preference for the fungal enzyme were identified. The selection of the target compounds for synthesis was partly guided by an automated docking and scoring procedure as well as molecular dynamics simulations. The modest selectivity of the synthesized inhibitors was reasonably well predicted, although a correct ranking of the relative affinities was not successful in all cases.

Pneumocystis jiroveci Pneumonia in Adult Patients with AIDS

Pneumocystis jiroveci (P. carinii) is an opportunistic pathogen that has gained particular prominence since the onset of the AIDS epidemic. Among several important advances in diagnosis and management, appropriately targeting chemoprophylaxis to HIV-infected patients at high clinical risk for P. jiroveci pneumonia and the introduction of effective combination anti-retroviral therapy (including highly active antiretroviral therapy [HAART]) have contributed to the reduced incidence of P. jiroveci pneumonia. Despite the success of these clinical interventions, P. jiroveci pneumonia remains the most common opportunistic pneumonia and the most common life-threatening infectious complication in HIV-infected patients. Trimethoprim/sulfamethoxazole (cotrimoxazole) remains the first-line agent for effective therapy and chemoprophylaxis, and corticosteroids represent an important adjunctive agent in the treatment of moderate-to-severe P. jiroveci pneumonia. However, problems of chemoprophylaxis and treatment failures, high rates of adverse drug reactions and drug intolerance to first-line antimicrobials, high rates of relapse or recurrence with second-line agents, and newer concerns about the development of P. jiroveci drug resistance represent formidable challenges to the management and treatment of AIDS-related P. jiroveci pneumonia. With the expanding global problem of HIV infection, the intolerance or unavailability of HAART to many individuals and limited access to healthcare for HIV-infected patients, P. jiroveci pneumonia will remain a major worldwide problem in the HIV-infected population. New drugs under development as anti-Pneumocystis agents such as echinocandins and pneumocandins, which inhibit beta-glucan synthesis, or sordarins, which inhibit fungal protein synthesis, show promise as effective agents. Continued basic research into the biology and genetics of P. jiroveci and host defense response to P. jiroveci will allow the development of newer antimicrobials and immunomodulatory therapeutic agents to more effectively treat life-threatening pneumonia caused by this organism.

Looking beyond highly active antiretroviral therapy: drug-related hepatotoxicity in patients with human immunodeficiency virus infection

Management of human immunodeficiency virus (HIV) has become increasingly complex since the introduction of highly active antiretroviral therapy (HAART). Patients with HIV have become exposed to an increasing array of drugs to treat HIV, prevent opportunistic infections and immune dysfunction, and manage comorbid illnesses and therapeutic complications. Hepatic complications have become common and may lead to discontinuation of treatment and significant morbidity. Up to 90% of patients with acquired immunodeficiency syndrome (AIDS) receive at least one drug that can cause hepatotoxicity. Clinicians treating patients with HIV frequently face difficulty distinguishing abnormal liver transaminase levels and toxicities in patients receiving several drugs. Some potential causes of hepatic dysfunction are viral infections, alcohol and substance abuse, and hepatotoxic drugs such as HAART. Recent reports have focused on the hepatotoxicity of HAART and the role of hepatitis viruses to the exclusion of many other agents prescribed for patients with HIV. Many of the common antibiotics, antifungals, antivirals, and ancillary agents prescribed for patients with HIV are independently associated with hepatotoxicity. Clinicians should be aware of the potential non-antiretroviral hepatotoxic agents that are frequently administered in HIV management.

Design, synthesis, computational prediction, and biological evaluation of ester soft drugs as inhibitors of dihydrofolate reductase from Pneumocystis carinii

A series of lipophilic soft drugs structurally related to the nonclassical dihydrofolate reductase (DHFR) inhibitors trimetrexate and piritrexim have been designed, synthesized, and evaluated in DHFR assays, with special emphasis on the inhibition of P. carinii DHFR. The best inhibitors, encompassing an ester bond in the bridge connecting the two aromatic systems, were approximately 10 times less potent than trimetrexate and piritrexim. The metabolites were designed to be poor inhibitors. Furthermore, molecular dynamics simulations of three ligands in complex with DHFR from Pneumocystis carinii and from the human enzyme were conducted in order to better understand the factors determining the selectivity. A correct ranking of the relative inhibition of DHFR was achieved utilizing the linear interaction energy method. The soft drugs are intended for local administration. One representative ester was selected for a pharmacokinetic study in rats where it was found to undergo fast metabolic degradation to the predicted inactive metabolites.

Dual pulmonary infection with Mycobacterium tuberculosis and Pneumocystis carinii in patients infected with human immunodeficiency virus

During a 22-month period, we identified 39 patients with human immunodeficiency virus (HIV) infection (mean CD4(+) count, 90 cells/mm(3)) who were hospitalized with pneumonia and who had sputum and/or other specimens that tested concurrently positive for both Mycobacterium tuberculosis and Pneumocystis carinii. The most common chest x-ray abnormality was a reticulonodular pattern or bilateral infiltrates (n=26). Serum lactate dehydrogenase levels were elevated in 17 (85%) of 20 of patients tested (mean value, 2208 U/L). Mean O(2) saturation and PO(2) were 89% and 64 mm Hg, respectively. A majority (24 patients [62%]) received both antituberculous and anti-PCP therapy (17 with steroids), and 22 improved. All ten patients who received no treatment for PCP improved and were discharged from the hospital, whereas 4 (80%) of the 5 persons who received no antituberculous treatment had a poor outcome (P<.001; OR=43). Patients with HIV or acquired immune deficiency syndrome may present with both TB and PCP; of the 2, TB seems to account for the most severe features of disease.

Management and Prevention of Opportunistic Infections in the HIV-Infected Patient

With the introduction of potent antiretroviral therapy, the incidence of opportunistic infections (OIs) as well as death has dramatically decreased since 1996. Opportunistic infections are seen mainly in three groups: (1) newly diagnosed patients not receiving antiretroviral therapy and presenting with an OI, (2) patients nonadherent to antiretroviral and OI treatment regimens or (3) patients whose antiretroviral therapy has failed. This article will review the most common opportunistic infections (OIs) seen in the HIV-infected individual and their treatment. The current guidelines for the prophylaxis against these OIs will also be discussed.

Expression and characterization of recombinant human-derived Pneumocystis carinii dihydrofolate reductase

Dihydrofolate reductase (DHFR) is the target of trimethoprim (TMP), which has been widely used in combination with sulfa drugs for treatment and prophylaxis of Pneumocystis carinii pneumonia. While the rat-derived P. carinii DHFR has been well characterized, kinetic studies of human-derived P. carinii DHFR, which differs from rat-derived P. carinii DHFR by 38% in amino acid sequence, have not been reported to date. Here we report on the expression and kinetic characterization of the recombinant human-derived P. carinii DHFR. The 618-bp coding sequence of the human-derived P. carinii DHFR gene was expressed in Escherichia coli. As determined by sodium dodecyl sulfate-polyacrylamide gel eletrophoresis, the purified enzyme had a molecular mass of 25 kDa, consistent with that predicted from the DNA sequence. Kinetic analysis showed that the K(m) values for dihydrofolate and NADPH were 2.7 +/- 0.3 and 14.0 +/- 4.3 microM, respectively, which are similar to those reported for rat-derived P. carinii DHFR. Inhibition studies revealed that both TMP and pyrimethamine were poor inhibitors of human-derived P. carinii DHFR, with K(i) values of 0.28 +/- 0.08 and 0.065 +/- 0.005 microM, respectively, while trimetrexate and methotrexate were potent inhibitors, with K(i) values of 0.23 +/- 0.03 and 0.016 +/- 0.004 nM, respectively. The availability of purified recombinant enzyme in large quantities should facilitate the identification of antifolate inhibitors with greater potency and higher selectivity for human-derived P. carinii DHFR.

Structure-based design of selective inhibitors of dihydrofolate reductase: synthesis and antiparasitic activity of 2, 4-diaminopteridine analogues with a bridged diarylamine side chain

As part of a larger search for potent as well as selective inhibitors of dihydrofolate reductase (DHFR) enzymes from opportunistic pathogens found in patients with AIDS and other immune disorders, N-[(2,4-diaminopteridin-6-yl)methyl]dibenz[b,f]azepine (4a) and the corresponding dihydrodibenz[b,f]azepine, dihydroacridine, phenoxazine, phenothiazine, carbazole, and diphenylamine analogues were synthesized from 2, 4-diamino-6-(bromomethyl)pteridine in 50-75% yield by reaction with the sodium salts of the amines in dry tetrahydrofuran at room temperature. The products were tested for the ability to inhibit DHFR from Pneumocystis carinii (pcDHFR), Toxoplasma gondii (tgDHFR), Mycobacterium avium (maDHFR), and rat liver (rlDHFR). The member of the series with the best combination of potency and species selectivity was 4a, with IC(50) values against the four enzymes of 0. 21, 0.043, 0.012, and 4.4 microM, respectively. The dihydroacridine, phenothiazine, and carbazole analogues were also potent, but nonselective. Of the compounds tested, 4a was the only one to successfully combine the potency of trimetrexate with the selectivity of trimethoprim. Molecular docking simulations using published 3D structural coordinates for the crystalline ternary complexes of pcDHFR and hDHFR suggested a possible structural interpretation for the binding selectivity of 4a and the lack of selectivity of the other compounds. According to this model, 4a is selective because of a unique propensity of the seven-membered ring in the dibenz[b,f]azepine moiety to adopt a puckered orientation that allows it to fit more comfortably into the active site of the P. carinii enzyme than into the active site of the human enzyme. Compound 4a was also evaluated for the ability to be taken up into, and retard the growth of, P. carinii and T. gondii in culture. The IC(50) of 4a against P. carinii trophozoites after 7 days of continuous drug treatment was 1.9 microM as compared with previously observed IC(50) values of >340 microM for trimethoprim and 0.27 microM for trimetrexate. In an assay involving [(3)H]uracil incorporation into the nuclear DNA of T. gondii tachyzoites as the surrogate endpoint for growth, the IC(50) of 4a after 5 h of drug exposure was 0.077 microM. The favorable combination of potency and enzyme selectivity shown by 4a suggests that this novel structure may be an interesting lead for structure-activity optimization.

Mechanisms of methotrexate resistance in acute leukemia. Decreased transport and polyglutamylation

Drug resistance limits the effectiveness of methotrexate (MTX) for the treatment of acute leukemia. An increased understanding of the pathways involved in folate metabolism has allowed investigations of the mechanisms of resistance observed in leukemic blasts obtained from patients. Acute lymphocytic leukemia (ALL) was studied for mechanisms of acquired MTX resistance. MTX transport in 27 patients with untreated ALL and 31 patients with relapsed ALL was measured using a previously described competitive displacement assay. Only 13% of the untreated patients were considered to have impaired MTX transport whereas over 70% of the relapsed patients had evidence of impaired MTX transport. Northern analyses and quantitative RT-PCR for the reduced folate carrier (RFC) were performed on the RNA available from the leukemic blasts of 24 patients in whom MTX transport had been measured. Six of 9 samples with impaired MTX transport had decreased RFC expression (one had no detectable RFC expression), while three had no decrease in RFC expression. Acute myelocytic leukemia (AML) was studied to determine the basis of the decreased MTX polyglutamylation. Enzyme kinetics of the enzyme folylpolyglutamate synthetase (FPGS) were studied, demonstrating FPGS in the myeloid cell lines and patient samples had a higher K(m) for MTX as a substrate than lymphoid cells. Measuring gamma-glutamyl hydrolase enzyme activity allowed a more accurate prediction of steady state levels of MTX polyglutamates. A knowledge of the mechanisms of MTX resistance that occur in leukemic blasts obtained from patients may allow the development of therapeutic strategies to circumvent resistance.

Escalating multiple-dose safety and tolerance study of oral WR 6026 in HIV-infected subjects: AIDS clinical trials group 173

WR 6026 is an 8-aminoquinoline with activity against Pneumocystis carinii in vitro and in an animal model of P. carinii pneumonia that has predicted the clinical utility of related compounds. This study was conducted to assess the safety and tolerance of WR 6026 given once daily for 21 days to HIV-infected subjects with CD4 counts <500 cells/microl. This double-blind, placebo-controlled study employed WR 6026 doses starting at 30 mg once daily and increasing to 60, 90, 120, or 150 mg once daily. Weekly visits for clinical and laboratory monitoring were conducted. Forty-nine study subjects, including 25 subjects with CD4 counts <200 cells/microl and 12 subjects with CD4 counts <100 cells/microl, entered the study. The maximum tolerated dose was 120 mg/day. Dose-limiting methemoglobinemia (>20%) was seen in 3 of 6 study subjects who received 150 mg/day for > or =19 days. Methemoglobin level was correlated with peak plasma WR 6026 concentrations. Three other study subjects developed skin rashes that may have been drug-related, and two developed asymptomatic serum triglyceride levels >1000 mg/dl. We conclude that WR 6026 is well tolerated at doses up to 120 mg/day for 21 days in HIV-infected volunteers including those with CD4 counts <200 cells/microl. Methemoglobinemia appears to be the primary dose-limiting toxicity.

Clearance of Pneumocystis carinii cysts in acute P carinii pneumonia: assessment by serial sputum induction

STUDY OBJECTIVES

To determine the feasibility of repeat sputum induction in acute Pneumocystis carinii pneumonia (PCP) and to define the rate of clearance of P carinii cysts from the respiratory tract of HIV-seropositive patients with acute PCP.

DESIGN

Prospective cohort evaluation.

SETTING

University medical center.

PARTICIPANTS

Twenty-four HIV-seropositive subjects with acute PCP.

MEASUREMENTS

Sputum induction for P carinii 2, 3, 4, and 6 weeks after initial diagnosis, and follow-up for 1 year.

RESULTS

Eighty-eight percent of subjects had residual cysts at 2 weeks, 76% at 3 weeks, 29% at 4 weeks, and 24% at 6 weeks postdiagnosis. A prior AIDS-defining illness (p = 0.033) or prior PCP (p = 0.004) predicted relapse within 6 months, but persistent cysts at 3 weeks did not; 8 of 16 sputum-positive subjects and 1 of 5 sputum-negative subjects experienced a relapse within 6 months (p = 0.34). Secondary prophylaxis with trimethoprim-sulfamethoxazole was associated with a reduced risk of relapse.

CONCLUSIONS

Serial sputum induction coupled with direct fluorescent antibody staining is a feasible, noninvasive method of respiratory tract surveillance for the eradication of P carinii during and after acute PCP. Three-quarters of HIV-seropositive patients with acute PCP have persistent cysts in their lungs at the end of antimicrobial treatment, despite clinical recuperation, but only one quarter have residual cysts 6 weeks postdiagnosis. A prior AIDS-defining illness and prior PCP are positively associated, and subsequent trimethoprim-sulfamethoxazole prophylaxis is negatively associated, with relapse within 6 months, while persistent organisms at 3 weeks do not appear to be a significant predictor of relapse risk.

Synthesis and biological activities of tricyclic conformationally restricted tetrahydropyrido annulated furo[2,3-d]pyrimidines as inhibitors of dihydrofolate reductases

The synthesis of seven 2,4-diamino-5,6,7,8-tetrahydro-7-substituted pyrido[4',3':4,5]furo[2,3-d]pyrimidines 1-6 are reported as nonclassical antifolate inhibitors of dihydrofolate reductase (DHFR) and compound 7 as a classical antifolate inhibitor of tumor cells in culture. The compounds were designed as conformationally restricted analogues of trimetrexate. The synthesis was accomplished from the cyclocondensation of 3-bromo-4-piperidone with 2, 4-diamino-6-hydroxypyrimidine to afford regiospecifically 2, 4-diamino-5,6,7,8-tetrahydropyrido[4',3':4,5]furo[2, 3-d]pyrimidine-7-hydrobromide (16). This in turn was alkylated with the appropriate benzyl halide to afford the target compounds 1-6. The classical antifolate 7 utilized 4-(chloromethyl)benzoyl-l-glutamic acid diethyl ester (17) instead of the benzyl halide for alkylation, followed by saponification to afford 7. Compounds 1-6 showed moderate inhibitory potency against DHFR from Pneumocystis carinii, Toxoplasma gondii, Mycobacterium avium, and rat liver. The classical analogue 7 was 88-fold more potent against M. avium DHFR than against rat liver DHFR. The classical analogue was also inhibitory against the growth of tumor cells, CCRF-CEM, and FaDu, in culture.

2,4-Diamino-6,7-dihydro-5H-cyclopenta[d]pyrimidine analogues of trimethoprim as inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase

Three previously unreported (R,S)-2,4-diamino-5-[(3,4,5-trimethoxyphenyl) alkyl]-6,7-dihydro-5H-cyclopenta[d]pyrimidines 15a-c were synthesized as analogues of trimethoprim (TMP) and were tested as inhibitors of Pneumocystis carinii, Toxoplasma gondii, and rat liver dihydrofolate reductase (DHFR). The length of the alkyl bridge between the cyclopenta[d]pyrimidine and trimethoxyphenyl moiety ranged from one in 15a to three carbons in 15c. The products were tested as competitive inhibitors of the reduction of dihydrofolate by Pneumocystis carinii, Toxoplasma gondii, and rat liver DHFR. Compounds 15a-c had IC50 values of > 32, 1.8 and 1.3 microM, respectively, against P. carinii DHFR, as compared to 12 microM for TMP. Against the T. gondii enzyme, 15a-c had IC50 values of 21, 0.14 and 0.14 microM, respectively, as compared to 2.7 microM for TMP. Inhibitors 15b and 15c with two- and three-carbon bridges were significantly more potent than 15a against all three enzymes. Unlike TMP, 15b and 15c were better inhibitors of the rat liver enzyme than of the microbial enzymes. The potency of 15b and 15c against rat liver DHFR was less than has been reported for the corresponding 6,7-dihydro-5H-cyclopenta[d]pyrimidines with a classical p-aminobenzoyl-L-glutamate side chain as inhibitors of bovine, murine, and human DHFR.

Acute respiratory failure in the HIV-seropositive patient

Since approximately 40% to 65% of patients with AIDS will develop pulmonary disease, HIV-seropositive patients represent a large cohort of immunosuppressed individuals with the potential to progress to respiratory failure requiring mechanical ventilation and admission to the intensive care unit. This article reviews the cause, pathophysiology, diagnostic approach, and management of acute respiratory failure requiring mechanical ventilation in HIV-seropositive patients. Prognostic factors and survival rates for episodes of respiratory failure are also discussed. In addition, an overview of acute respiratory failure in pediatric AIDS patients is presented.

Care for the patient with AIDS in the ICU: outcomes and ethics

HIV infection and AIDS are common diagnoses in many intensive care units (ICUs) in the United States. Although Pneumocystis carinii currently represents only one quarter of all diagnoses for which HIV-infected persons are admitted to the ICU, it is the disease with the most clinically applicable outcome data and, therefore, is a model for ethical decision-making regarding patients with HIV infection in the ICU. Despite advances in diagnosis and treatment of HIV-related P. carinii, recent studies show that only 20% to 25% of the patients with acute respiratory failure survive to hospital discharge. Although many clinical markers correlate with survival, none of the individual markers or prediction scoring systems have the accuracy needed in clinical practice. One goal of predicting outcome in the ICU is to aid both the patient and the physician in making decisions about when to pursue aggressive therapy and when to withhold or withdraw such therapy. Because our ability to predict outcome is limited, advance directives and communication with patients and families about end-of-life medical care are of utmost importance. Even though it is not always possible for patients to predict, in advance, what they would want done in various hypothetical health care scenarios, quality communication between physicians, patients, and families with realistic discussion of outcomes and maintenance of hope and dignity can facilitate decisions about the use of intensive care for patients with AIDS.

Pneumocystis carinii

Improved understanding of Pneumocystis carinii, in particular the widespread use of chemoprophylaxis, has resulted in a declining incidence of infection in patients infected with HIV since the late 1980s. Despite these advances, P. carinii pneumonia continues to represent an important cause of pulmonary disease in HIV-seropositive individuals who do not receive chemoprophylaxis or when breakthrough episodes occur. This article reviews the history, biology, clinical manifestations, prognostic markers, therapy, and chemoprophylaxis of P. carinii pneumonia in HIV-seropositive patients.

AIDS and the lung

Respiratory symptoms are common in HIV-infected persons. The challenge facing clinicians is to determine whether these respiratory symptoms are due to an opportunistic infection or to a chronic process, such as asthma, chronic bronchitis, bronchiectasis, or emphysema. This article reviewed the clinical presentation, diagnosis, and treatment of two important opportunistic infections, PCP and bacterial pneumonia. It also reviewed the current data on obstructive lung diseases as they relate to HIV.

Monodrug efficacies of sulfonamides in prophylaxis for Pneumocystis carinii pneumonia

A remarkably high rate of adverse events is associated with the use of trimethoprim-sulfamethoxazole in patients with human immunodeficiency virus type 1 infection. We examined the efficacies of sulfonamides alone in the prevention of Pneumocystis carinii pneumonitis, with the assumption that at least some of the adverse events with the drug combination might be due to trimethoprim. With the immunosuppressed rat model, eight sulfonamides were studied at 100, 10, and 1.0 mg/kg/day (10 rats per dosage and drug). P. carinii infection was prevented in all animals (100%) receiving dosages of as little as 1.0 mg of sulfamethoxazole, sulfamethoxypyridazine, and sulfadimethoxine per kg per day, as little as 10 mg of sulfameter, sulfachlorpyridazine, and sulfaquinoxaline per kg per day; and 100 mg of sulfaguanidine and sulfanilamide per kg per day. These studies suggest that a sulfonamide, such as sulfamethoxazole, might provide effective prophylaxis for P. carinii pneumonitis without trimethoprim.

Molecular docking towards drug discovery

Fueled by advances in molecular structure determination, tools for structure-based drug design are proliferating rapidly. Lead discovery through searching of ligand databases with molecular docking techniques represents an attractive alternative to high-throughout random screening. The size of commercial databases imposes severe computational constraints on molecular docking, compromising the level of calculational detail permitted for each putative ligand. We describe alternative philosophies for docking which effectively address this challenge. With respect to the dynamic aspects of molecular recognition, these strategies lie along a spectrum of models bounded by the Lock-and-Key and Induced-Fit theories for ligand binding. We explore the potential of a rigid model in exploiting species specificity and of a tolerant model in predicting absolute ligand binding affinity. Current molecular docking methods are limited primarily by their ability to rank docked complexes; we therefore place particular emphasis on this aspect of the problem throughout our validation of docking strategies.

High-affinity inhibitors of dihydrofolate reductase: antimicrobial and anticancer activities of 7,8-dialkyl-1,3-diaminopyrrolo[3,2-f]quinazolines with small molecular size

A series of 7,8-dialkylpyrrolo[3,2-f]quinazolines were prepared as inhibitors of dihydrofolate reductase (DHFR). On the basis of an apparent inverse relationship between compound size and antifungal activity, the compounds were designed to be relatively small and compact. Inhibitor design was aided by GRID analysis of the three-dimensional structure of Candida albicans DHFR, which suggested that relatively small, branched alkyl groups at the 7- and 8-positions of the pyrroloquinazoline ring system would provide optimal interactions with a hydrophobic region of the protein. The compounds were potent inhibitors of fungal and human DHFR, with K(i) values as low as 7.1 and 0.1 pM, respectively, and were highly active against C. albicans and an array of tumor cell lines. In contrast to known lipophilic inhibitors of DHFR such as trimetrexate and piritrexim, members of this series of pyrroloquinazolines were not susceptible to P-glycoprotein-mediated multidrug resistance and also showed significant distribution into lung and brain tissue. The compounds were active in lung and brain tumor models and displayed in vivo activity against Pneumocystis carinii and C. albicans.

Antifolates: current developments

In summary, the problem of MTX resistance has been approached in a mechanistic fashion, based on the wealth of information generated over the years. To date, these strategies have produced several new classes of anticancer drugs, with a variety of anticipated and unanticipated mechanisms of action. Several of these have shown promising preclinical activity, and these are moving into more stringent testing in the clinic.

Resistance mechanisms to methotrexate in tumors

The mechanisms of intrinsic and acquired resistance to methotrexate (MTX) in human tumors are reviewed herein. In blasts from patients with acute lymphocytic leukemia, resistance mechanisms found are decreased uptake and increased dihydrofolate reductase (DHFR) activity. A major cause of intrinsic resistance to MTX in soft tissue sarcoma cells and in acute myelocytic leukemia appears to be a lack of drug retention, due mainly to low levels of polyglutamylation. A novel association between lack of the retinoblastoma protein and intrinsic MTX resistance has been found. This has been attributed to an increase in DHFR activity, due to an increased rate of transcription of this gene, stimulated by an increase in levels of free E2F, not sequestered by hypophosphorylated retinoblastoma protein.

Protection and rescue from 2',3'-dideoxypyrimidine nucleoside analog toxicity by hemin in human bone marrow progenitor cells

Long-term therapy of AIDS patients with 3'-azido-3'-deoxythymidine (AZT) remains of concern because of resulting hematopoietic toxicity. While the mechanism(s) of this toxicity remains elusive, alternative strategies are being developed to reduce these toxic effects, including combination therapy with nonmyelotoxic antihuman immunodeficiency virus drugs and/or administration of protective or rescue agents, including cytokines and growth factors. By using a particularly relevant human CD34+ liquid culture system, the unique profiles of dideoxynucleoside (ddN) toxicities to both proliferation and differentiation were demonstrated, with decreased potencies in the order of 3'-fluoro-3'-deoxythymidine (FLT) = 3'-amino-3'-deoxythymidine (AMT) = 2',3'-dideoxycytidine > AZT for inhibition of proliferation and in the order of FLT = AMT > AZT >> 2',3'-dideoxycytidine for inhibition of hemoglobin synthesis. Hemin selectively protected erythroid-lineage human burst-forming unit-erythroid cells from AZT- and AMT-induced inhibition but had no effect on FLT toxicity under similar conditions. Myeloid-lineage human CFU-granulocyte-macrophages were also not protected by hemin against all three ddN analogs. The simultaneous exposure of cells to hemin and AZT resulted in a complete protection of both cell proliferation and hemoglobin synthesis. In contrast, in reversal studies only the inhibition of the percentage of hemoglobin-synthesizing cells returned to control levels, but the inhibition of proliferation of cells previously exposed to AZT was not reversed by hemin. These studies further define the unique and multifactorial mechanism(s) of ddN-induced toxic effects during hematopoietic development of pluripotent stem cells and suggest that the use of hemin could be beneficial in alleviating the toxicity of certain ddN analogs.

[Pneumocystis carinii pneumonia in AIDS: retrospective analysis of 80 documented cases (1985-1993)]

Eighty initial episodes of HIV-associated Pneumocystis carinii pneumonia (PCP) diagnosed at Bordeaux hospital between 1985 and 1993 are reported (57 were men and 23 women). PCP revealed HIV infection in 29 patients (36%). Others cases were patients with poor medical follow up (10%), with a CD4+ lymphocyte count above 200/mm3 at last follow-up (9%), non compliant with PCP prophylaxis (9%), or using aerolized pentamidine (AP+) (20%). The main clinical symptoms were fever (90%), dyspnea (68%), non productive (63%) and productive (17%) cough. Radiographic infiltrates were purely interstitial (59%), acinar and interstitial (25%), purely acinar (5%) and absent (11%). Thirty-eight percent of AP+ had upper lobe preferential involvement and 13% a pleural effusion. In all cases, Pneumocystis carinii was detected in bronchoalveolar lavage. Extrapulmonary localizations of pneumocystosis were noticed (eye, liver, spleen, ascitis) in two AP+. Mean CD4+ count was 54/mm3 in patients not having received aerolized pentamidine (AP-) and 22/mm3 in AP+. P24 antigenemia was positive in 53% (AP-) and 88% (AP+). PaO2 LDH and albuminemia were similar in both groups. Antimicrobial therapy (Cotrimoxazole in 91% of the cases) was combined with corticosteroids in 45% and mechanic ventilation in 19%. After 30 days of follow-up, 17 deaths were observed (21%) and 14 attributed to PCP: mortality was worse in AP+ (31%) than in AP- (19%). The main conclusions of our study are the followings: HIV related PCP is still in 1995 frequent and severe; atypical features should not rule out diagnosis; preventive measures are neither sufficient nor efficient. PCP remains in 1995 a priority in HIV related public health and therapeutical research.