Trimetrexate with leucovorin versus trimethoprim-sulfamethoxazole for moderate to severe episodes of Pneumocystis carinii pneumonia in patients with AIDS: a prospective, controlled multicenter investigation of the AIDS Clinical Trials Group Protocol 029/031

Comparative efficacy and safety of treatment regimens for Pneumocystis jirovecii pneumonia in people living with HIV: a systematic review and network meta-analysis of randomized controlled trials

BACKGROUND

Pneumocystis jirovecii pneumonia (PCP) is a serious opportunistic infection in people living with HIV (PWH) who have low CD4 counts. Despite its side effects, trimethoprim-sulfamethoxazole (TMP-SMX) is currently considered the primary treatment for PCP.

OBJECTIVES

The objectives of this study are to compare the efficacy (treatment failure and mortality) and tolerability (treatment change) of PCP treatment regimens with a frequentist network meta-analysis.

DATA SOURCES

Data sources include Embase, Medline, and CENTRAL from inception to 3 February 2024.

STUDY ELIGIBILITY CRITERIA

Study eligibility criteria include comparative randomized controlled trials (RCTs) of at least two PCP treatment regimens.

PARTICIPANTS

Participants include PWH.

INTERVENTIONS

Interventions include treatment regimens for PCP compared head-to-head.

ASSESSMENT OF RISK OF BIAS

Assessment of risk of bias includes Cochrane Risk-of-bias tool for RCTs (Cochrane Risk-of-Bias 2).

METHODS OF DATA SYNTHESIS

Title, abstract, and full-text screening, along with data extraction, were conducted by two independent reviewers. Data on PCP treatment failure, all-cause mortality, and discontinuation because of toxicity were pooled and ranked.

RESULTS

Fourteen RCTs conducted between 1983 and 1996 included 1788 participants across 27 treatment arms. No regimen showed statistically significant superiority over TMP-SMX in direct comparison. In the network meta-analysis, clindamycin/primaquine was ranked the best (surface under the cumulative ranking curve, 0.8), followed by intravenous pentamidine (0.8) and TMP-SMX (0.8) regarding treatment failure. Regarding all-cause mortality, TMP-SMX was superior to atovaquone in direct comparison, but no treatment was superior in the full network analysis. Dapsone-TMP (0.7) and intravenous pentamidine (0.8) were ranked the highest for mortality reduction. For safety and tolerability, comparator drugs consistently outperformed TMP-SMX, with significant reductions in toxicity observed for dapsone-TMP, inhaled pentamidine, and atovaquone. Inhaled pentamidine (0.9) was the best tolerated, followed by trimetrexate (0.8) and atovaquone (0.8).

CONCLUSIONS

We conclude that TMP-SMX should be reassessed as the standalone first-line therapy for PCP in PWH, given the better tolerability and comparable efficacy of other treatments. In places with access to alternative drugs for PCP treatment, our analysis suggests that alternative regimens may offer comparable effectiveness, providing flexibility to use alternative treatments when comorbidities necessitate it.

Low-dose trimethoprim-sulfamethoxazole for the treatment of Pneumocystis jirovecii pneumonia (LOW-TMP): protocol for a phase III randomised, placebo-controlled, dose-comparison trial

INTRODUCTION

Pneumocystis jirovecii pneumonia (PJP) is an opportunistic infection of immunocompromised hosts with significant morbidity and mortality. The current standard of care, trimethoprim-sulfamethoxazole (TMP-SMX) at a dose of 15-20 mg/kg/day, is associated with serious adverse drug events (ADE) in 20%-60% of patients. ADEs include hypersensitivity reactions, drug-induced liver injury, cytopenias and renal failure, all of which can be treatment limiting. In a recent meta-analysis of observational studies, reduced dose TMP-SMX for the treatment of PJP was associated with fewer ADEs, without increased mortality.

METHODS AND ANALYSIS

A phase III randomised, placebo-controlled, trial to directly compare the efficacy and safety of low-dose TMP-SMX (10 mg/kg/day of TMP) with the standard of care (15 mg/kg/day of TMP) among patients with PJP, for a composite primary outcome of change of treatment, new mechanical ventilation, or death. The trial will be undertaken at 16 Canadian hospitals. Data will be analysed as intention to treat. Primary and secondary outcomes will be compared using logistic regression adjusting for stratification and presented with 95% CI.

ETHICS AND DISSEMINATION

This study has been conditionally approved by the McGill University Health Centre; Ethics approval will be obtained from all participating centres. Results will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04851015.

On the Treatment of Pneumocystis jirovecii Pneumonia: Current Practice Based on Outdated Evidence

Pneumocystis jirovecii pneumonia (PCP) is a common opportunistic infection causing more than 400000 cases annually worldwide. Although antiretroviral therapy has reduced the burden of PCP in persons with human immunodeficiency virus (HIV), an increasing proportion of cases occur in other immunocompromised populations. In this review, we synthesize the available randomized controlled trial (RCT) evidence base for PCP treatment. We identified 14 RCTs that were conducted 25-35 years ago, principally in 40-year-old men with HIV. Trimethoprim-sulfamethoxazole, at a dose of 15-20 mg/kg per day, is the treatment of choice based on historical practice rather than on quality comparative, dose-finding studies. Treatment duration is similarly based on historical practice and is not evidence based. Corticosteroids have a demonstrated role in hypoxemic patients with HIV but have yet to be studied in RCTs as an adjunctive therapy in non-HIV populations. The echinocandins are potential synergistic treatments in need of further investigation.

Pneumocystis jirovecii: a review with a focus on prevention and treatment

Introduction: Pneumocystis jirovecii (PJ) is an opportunistic fungal pathogen that can cause severe pneumonia in immunocompromised hosts. Risk factors for Pneumocystis jirovecii pneumonia (PJP) include HIV, organ transplant, malignancy, certain inflammatory or rheumatologic conditions, and associated therapies and conditions that result in cell-mediated immune deficiency. Clinical signs of PJP are nonspecific and definitive diagnosis requires direct detection of the organism in lower respiratory secretions or tissue. First-line therapy for prophylaxis and treatment remains trimethoprim-sulfamethoxazole (TMP-SMX), though intolerance or allergy, and rarely treatment failure, may necessitate alternate therapeutics, such as dapsone, pentamidine, atovaquone, clindamycin, primaquine and most recently, echinocandins as adjunctive therapy. In people living with HIV (PLWH), adjunctive corticosteroid use in treatment has shown a mortality benefit.Areas covered: This review article covers the epidemiology, pathophysiology, diagnosis, microbiology, prophylaxis indications, prophylactic therapies, and treatments.Expert opinion: TMP-SMX has been first-line therapy for treating and preventing pneumocystis for decades. However, its adverse effects are not uncommon, particularly during treatment. Second-line therapies may be better tolerated, but often sacrifice efficacy. Echinocandins show some promise for new combination therapies; however, further studies are needed to define optimal antimicrobial therapy for PJP as well as the role of corticosteroids in those without HIV.

Low-Dose TMP-SMX in the Treatment of Pneumocystis jirovecii Pneumonia: A Systematic Review and Meta-analysis

Background

Pneumocystis jirovecii pneumonia (PJP) remains a common and highly morbid infection for immunocompromised patients. Trimethoprim-sulfamethoxazole (TMP-SMX) is the antimicrobial treatment of choice. However, treatment with TMP-SMX can lead to significant dose-dependent renal and hematologic adverse events. Although TMP-SMX is conventionally dosed at 15–20 mg/kg/d of trimethoprim for the treatment of PJP, reduced doses may be effective and carry an improved safety profile.

Methods

We conducted a systematic search in the Medline, Embase, and Cochrane Library databases from inception through March 2019 for peer-reviewed studies reporting on reduced doses of TMP-SMX (15 mg/kg/d of trimethoprim or less) for the treatment of PJP. PRISMA, MOOSE, and Cochrane guidelines were followed. Gray literature was excluded.

Results

Ten studies were identified, and 6 were included in the meta-analysis. When comparing standard doses with reduced doses of TMP-SMX, there was no statistically significant difference in mortality (absolute risk difference, –9% in favor of reduced dose; 95% confidence interval [CI], –27% to 8%). When compared with standard doses, reduced doses of TMP-SMX were associated with an 18% (95% CI, –31% to –5%) absolute risk reduction of grade ≥3 adverse events.

Conclusions

In this systematic review, treatment of PJP with doses of ≤10 mg/kg/d of trimethoprim was associated with similar rates of mortality when compared with standard doses and with significantly fewer treatment-emergent severe adverse events. Although limited by the observational nature of the studies included, this review provides the most current available evidence for the optimal dosing of TMP-SMX in the treatment of PJP.

Effectiveness and safety of lower dose sulfamethoxazole/trimethoprim therapy for Pneumocystis jirovecii pneumonia in patients with systemic rheumatic diseases: A retrospective multicenter study

OBJECTIVES

To evaluate the effectiveness and safety of lower-dose sulfamethoxazole/trimethoprim therapy (SMX/TMP) for Pneumocystis jirovecii pneumonia (PCP) in patients with systemic rheumatic diseases.

METHODS

In this multicenter retrospective study, we compared effectiveness and safety of SMX/TMP for the treatment of PCP among patients divided into three groups according to the initial dosage of SMX/TMP: the low, ≤10 mg/kg/day; the intermediate, 10-15 mg/kg/day; and the high and conventional, 15-20 mg/kg/day for TMP dose.

RESULTS

Eighty-one patients, including 22, 30, and 29 patients in the low-, the intermediate- and the high-dose group could be analyzed and the 30-day survival rate were 100%, 93.3%, and 96.7%, respectively (P = 0.28). There were significant dose-dependent increasing trends of severe adverse drug reactions (ADRs) for SMX/TMP that were graded as ≥3 according to the Common Terminology Criteria for Adverse Events. When stratified by presence of severe hypoxemia defined by alveolar-arterial O2 gradient ≥45 mmHg, the 30-day survival and treatment modification rate were similar among the three groups, but frequency of severe ADRs were significantly decreased in the low-dose group. The low-dose group was independently and negatively associated with treatment modification within 14 days and severe ADRs.

CONCLUSIONS

Lower dose SMX/TMP therapy with ≤10 mg/kg/day for TMP was as effective as higher dose therapy for the treatment of PCP and associated with lower rates of treatment modification and severe ADRs in patients with systemic rheumatic diseases.

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.

A Review of Pneumocystis Pneumonia

Pneumocystis pneumonia remains one of the leading causes of morbidity and mortality in the HIV-infected population. Trimethoprim-sulfamethoxazole remains the drug of choice for both the treatment and prevention of this infection, although a high rate of side effects in HIV-infected patients often necessitates alternative treatment regimens. This article will review pneumocystis pneumonia, with a focus on the various therapeutic options, their side effects, and the immune reconstitution inflammatory syndrome as it relates to pneumocystis pneumonia infection.

Treatment of Pneumocystis pneumonia with intermediate-dose and step-down to low-dose trimethoprim-sulfamethoxazole: lessons from an observational cohort study

Background

The recommended treatment of Pneumocystis jirovecii pneumonia (PCP) is high-dose trimethoprim–sulfamethoxazole (TMP–SMX) in an equivalent of TMP 15–20 mg/kg/day and SMX 75–100 mg/kg/day for 2 or 3 weeks. High rates of adverse events are reported with this dose, which raises the question if lower doses are possible.

Methods

All adult patients diagnosed with PCP in various immune dysfunctions and treated with TMP–SMX between January 1, 2003 and July 1, 2013 in a tertiary university hospital were included. Per institutional protocol, patients initiated treatment on intermediate-dose TMP–SMX (TMP 10–15 mg/kg/day) and could be stepped down to low-dose TMP–SMX (TMP 4–6 mg/kg/day) during treatment. Clinical variables at presentation, relapse rate and mortality rates were compared between intermediate- and step-down treatment groups by uni- and multivariate analyses.

Results

A total of 104 patients were included. Twenty-four patients (23 %) were switched to low-dose TMP–SMX after a median of 4.5 days (IQR 2.8–7.0 days). One relapse (4 %) occurred in the step-down group versus none in the intermediate-dose group. The overall 30-day mortality was 13 %. There was 1 death in the step-down group (4 %) compared to 13 deaths (16 %) in the intermediate-dose group.

Conclusions

We observed high cure rates of PCP by treatment with intermediate-dose TMP–SMX. In addition, a step-down strategy to low-dose TMP–SMX during treatment in selected patients appears to be safe and does not compromise the outcome of treatment.

Pneumocystis jirovecii colonization in Chronic Obstructive Pulmonary Disease (COPD)

Chronic obstructive pulmonary disease (COPD) is associated with a chronic inflammatory response in airways and lung parenchyma that results in significant morbidity and mortality worldwide. Cigarette smoking considered as an important risk factor plays a role in pathogenesis of disease. Pneumocystis jirovecii is an atypical opportunistic fungus that causes pneumonia in immunosuppressed host, although the low levels of its DNA in patients without signs and symptoms of pneumonia, which likely represents colonization. The increased prevalence of P. jirovecii colonization in COPD patients has led to an interest in understanding its role in the disease. P. jirovecii colonization in these patients could represent a problem for public health since colonized patients could act as a major reservoir and source of infection for susceptible subjects. Using sensitive molecular techniques, low levels of P. jirovecii DNA have been detected in the respiratory tract of certain individuals. It is necessary to elucidate the role of P. jirovecii colonization in the natural history of COPD patients in order to improve the clinical management of this disease. In the current review paper, we discuss P. jirovecii colonization in COPD patients.

Design, synthesis, and molecular modeling of novel pyrido[2,3-d]pyrimidine analogues as antifolates; application of Buchwald-Hartwig aminations of heterocycles

Opportunistic infections caused by Pneumocystis jirovecii (P. jirovecii, pj), Toxoplasma gondii (T. gondii, tg), and Mycobacterium avium (M. avium, ma) are the principal causes of morbidity and mortality in patients with acquired immunodeficiency syndrome (AIDS). The absence of any animal models for human Pneumocystis jirovecii pneumonia and the lack of crystal structures of pjDHFR and tgDHFR make the design of inhibitors challenging. A novel series of pyrido[2,3-d]pyrimidines as selective and potent DHFR inhibitors against these opportunistic infections are presented. Buchwald-Hartwig coupling reaction of substituted anilines with pivaloyl protected 2,4-diamino-6-bromo-pyrido[2,3-d]pyrimidine was successfully explored to synthesize these analogues. Compound 26 was the most selective inhibitor with excellent potency against pjDHFR. Molecular modeling studies with a pjDHFR homology model explained the potency and selectivity of 26. Structural data are also reported for 26 with pcDHFR and 16 and 22 with variants of pcDHFR.

Systematic review on the etiology and antibiotic treatment of pneumonia in human immunodeficiency virus-infected children

BACKGROUND

Community-acquired pneumonia (CAP) is a leading cause of morbidity and mortality in human immunodeficiency virus (HIV)-infected children.

OBJECTIVES AND METHODS

A systematic review of studies that were published between January 1990 and February 2009 on the etiology and antimicrobial or adjunctive systemic management of CAP in HIV-infected children.

RESULTS

Pneumocystis jirovecii had the strongest association with HIV infection, with a summary odds ratio of 10.1 (95% confidence interval [CI], 17.7-62.1) and 9.1 (95% CI, 2.5-33.1) in antemortem and postmortem studies, respectively. Cytomegalovirus was strongly associated with HIV positivity among fatal cases of pneumonia (summary odds ratio = 14.4 [95% CI, 6.7-30.8]). There was a trend toward a greater prevalence of Staphylococcus aureus (odds ratio, 2.5; 95% CI, 0.95-6.4) in HIV-infected children. Major limitations identified included substantial methodological heterogeneity across studies, limited sensitivity of assays for diagnosing bacterial pneumonia, and studies primarily being undertaken in the absence of antiretroviral treatment or cotrimoxazole prophylaxis. No a priori-planned randomized controlled trials on antimicrobial management of CAP in HIV-infected children were identified.

CONCLUSIONS

A World Health Organization panel used this review as well as analysis of risks and benefits to revise recommendations for antimicrobial treatment of CAP. Ampicillin plus gentamicin or ceftriaxone is now recommended as first-line empiric regimens for treating severe and very severe CAP in HIV-infected children. In addition, treatment with cloxacillin or vancomycin is recommended in settings with a high incidence of methicillin-resistant S. aureus, and particularly if clinical or microbiological evidence of S. aureus pneumonia exist. Further studies in HIV-infected children on CAP etiology and antibiotic treatment are required in the era of antiretroviral treatment.

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.

Pafuramidine for Pneumocystis jiroveci pneumonia in HIV-infected individuals

Pneumocystis jiroveci pneumonia remains one of the major worldwide contributors to the morbidity and mortality of those with HIV infection. The mainstay of therapy for treatment is trimethoprim-sulfamethoxazole (TMP-SMX); however TMP-SMX may be associated with significant side effects and intolerability. In addition, TMP-SMX has a moderate pill burden with three- to four-times daily dosing schedule. Patients unable to tolerate TMP-SMX are confronted with either parenteral therapy or other oral agents that may be less efficacious or are associated with potential serious adverse reactions. Pafuramidine (DB289) is an orally bioavailable prodrug of furamidine (DB75), an investigational diamidine that is less toxic than previous diamidines such as pentamidine. To date, human trials suggest that pafuramidine is well tolerated overall and has clinical activity against Pneumocystis pneumonia. In this article, we review the available data for the use of pafuramidine in Pneumocystis pneumonia.

Management of Pneumocystis jiroveci pneumonia in children receiving chemotherapy

Pneumocystis jiroveci (formerly carinii) pneumonia (PCP) is a serious opportunistic infection in children and adolescents with cancer. It was the most common cause of death among children receiving chemotherapy prior to the inclusion of PCP prophylaxis as part of standard care for children with leukemia. The incidence of PCP has decreased significantly since initiation of prophylaxis; however, breakthrough cases continue to occur. Hematologic malignancies, brain tumors necessitating prolonged corticosteroid therapy, hematopoietic stem cell transplantation, prolonged neutropenia, and lymphopenia are the most important risk factors for PCP in children not infected with HIV. Of children with leukemia, 15-20% may develop PCP in the absence of prophylaxis. Infection with P. jiroveci occurs early in life in most individuals. However, clinically apparent disease occurs almost exclusively in immunocompromised persons. Dyspnea, cough, hypoxia, and fever are the most common presenting symptoms of PCP. Chest radiography and high-resolution CT scans of the chest demonstrate a characteristic ground-glass pattern. Induced sputum analysis and bronchoalveolar lavage are the diagnostic procedures of choice. Gomori's methenamine-silver stain, Geimsa or Wright's stain, and monoclonal immunofluorescent antibody stains are most commonly used to make a diagnosis. However, identification of P. jiroveci DNA using polymerase chain reaction assays in bronchoalveolar lavage fluid is more sensitive. Trimethoprim-sulfamethoxazole (TMP-SMZ; cotrimoxazole) is the recommended drug for the treatment of PCP. Patients who are intolerant of TMP-SMZ or who have not responded to treatment after 5-7 days of therapy with TMP-SMZ should be treated with pentamidine. A short course of corticosteroids is recommended for moderate to severe cases of PCP within the first 72 hours after diagnosis. Mutations in the dihydropteroate synthetase gene may confer resistance to TMP-SMZ; however, the clinical relevance of these mutations is not well established. TMP-SMZ is the most commonly used agent for prophylaxis. Myelosuppression is the most important adverse effect of TMP-SMZ and the most frequent cause for choosing alternative prophylactic agents in children undergoing chemotherapy. Alternative agents for chemoprophylaxis include dapsone, aerosolized pentamidine, and atovaquone. Alternative prophylactic agents must be used in patients developing myelosuppression secondary to TMP-SMZ or dapsone.

Critical care of immunocompromised patients: human immunodeficiency virus

OBJECTIVE

To describe critical illnesses that occur commonly in patients with human immunodeficiency virus (HIV) infection.

METHODS

We reviewed and summarized the literature on critical illness in HIV infection using a computerized MEDLINE search.

SUMMARY

In the last 10 yrs, our perception of HIV infection and acquired immune deficiency syndrome (AIDS) has changed from an almost uniformly fatal disease into a manageable chronic illness. Even patients with advanced immunosuppression may have prolonged survival, although usually with exacerbations and remissions, complicated by therapy-related toxicity and medical and psychiatric co-morbidity. The prevalence of opportunistic infections and the mortality have decreased considerably since early in the epidemic. The most common reason for intensive care unit admission in patients with AIDS is respiratory failure, but they are less likely to be admitted for Pneumocystis pneumonia and other HIV-associated opportunistic infections. HIV-infected persons are more likely to receive intensive care unit care for complications of end-stage liver disease and sepsis. Hepatitis C has emerged as a common cause of morbidity and mortality in patients with HIV infection. In addition, some develop life-threatening complications from antiretroviral drug toxicity and the immune reconstitution inflammatory syndrome.

Antiparasitic therapy in children

Treatment of parasitic infections in children presents many challenges for the clinician. Although parasitic infections are ubiquitous on a worldwide basis, with an estimated 1 billion persons infected with intestinal helminthes alone, physicians in the United States and other developed countries are often unfamiliar with the management of these diseases. Children are traveling internationally in larger numbers than ever before, however, and emigration from developing countries to the United States and other Western countries is increasing, so clinicians in these countries are confronted more frequently with parasitic diseases from the tropics. This article describes current approaches to antiparasitic therapy. Drugs used in the treatment of more than one type of parasite are presented once in detail, with reference to the detailed description in subsequent sections.

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.

Synthesis of 2,4-Diamino-6-[2‘-O-(ω-carboxyalkyl)oxydibenz[b,f]azepin-5-yl]methylpteridines as Potent and Selective Inhibitors of Pneumocystis carinii, Toxoplasma gondii, and Mycobacterium avium Dihydrofolate Reductase

Six previously undescribed N-(2,4-diaminopteridin-6-yl)methyldibenz[b,f]azepines with water-solubilizing O-carboxyalkyloxy or O-carboxybenzyloxy side chains at the 2'-position were synthesized and compared with trimethoprim (TMP) and piritrexim (PTX) as inhibitors of dihydrofolate reductase (DHFR) from Pneumocystis carinii (Pc), Toxoplasma gondii (Tg), and Mycobacterium avium (Ma), three of the opportunistic organisms known to cause significant morbidity and mortality in patients with AIDS and other disorders of the immune system. The ability of the new analogues to inhibit reduction of dihydrofolate to tetrahydrofolate by Pc, Tg, Ma, and rat DHFR was determined, and the selectivity index (SI) was calculated from the ratio IC(50)(rat DHFR)/IC(50)(Pc, Tg, or Ma DHFR). The IC(50) values of the 2'-O-carboxypropyl analogue (10), with SI values in parentheses, were 1.1 nM (1300) against Pc DHFR, 9.9 nM (120) against Tg DHFR, and 2.0 nM (600) against Ma DHFR. The corresponding values for the 2'-O-(4-carboxybenzyloxy) analogue (12) were 1.0 nM (560), 22 nM (21), and 0.75 nM (630). By comparison, the IC(50) and SI values for TMP were Pc, 13 000 nM (14); Tg, 2800 nM (65); and Ma, 300 nM (610). For the prototypical potent but nonselective inhibitors PTX and TMX, respectively, these values were Pc, 13 nM (0.26) and 47 nM (0.17); Tg, 4.3 nM (0.76) and 16 nM (0.50); Ma, 0.61 nM (5.4) and 1.5 nM (5.3). Thus 10 and 12 met the criterion for DHFR inhibitors that combine the high selectivity of TMP with the high potency of PTX and TMX.

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.

Pneumocystis carinii pneumonia in patients with and without HIV infection

Advances in the prevention and treatment of Pneumocystis carinii pneumonia in HIV infected patients have led to a decrease in the incidence and improved outcomes. Pneumocystis carinii pneumonia continues to be problematic in non-HIV infected immunocompromised patients.

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.

Dicyclic and tricyclic diaminopyrimidine derivatives as potent inhibitors of Cryptosporidium parvum dihydrofolate reductase: structure-activity and structure-selectivity correlations

A structurally diverse library of 93 lipophilic di- and tricyclic diaminopyrimidine derivatives was tested for the ability to inhibit recombinant dihydrofolate reductase (DHFR) cloned from human and bovine isolates of Cryptosporidium parvum (J. R. Vásquez et al., Mol. Biochem. Parasitol. 79:153-165, 1996). In parallel, the library was also tested against human DHFR and, for comparison, the enzyme from Escherichia coli. Fifty percent inhibitory concentrations (IC(50)s) were determined by means of a standard spectrophotometric assay of DHFR activity with dihydrofolate and NADPH as the cosubstrates. Of the compounds tested, 25 had IC(50)s in the 1 to 10 microM range against one or both C. parvum enzymes and thus were not substantially different from trimethoprim (IC(50)s, ca. 4 microM). Another 25 compounds had IC(50)s of <1.0 microM, and 9 of these had IC(50)s of <0.1 microM and thus were at least 40 times more potent than trimethoprim. The remaining 42 compounds were weak inhibitors (IC(50)s, >10 microM) and thus were not considered to be of interest as drugs useful against this organism. A good correlation was generally obtained between the results of the spectrophotometric enzyme inhibition assays and those obtained recently in a yeast complementation assay (V. H. Brophy et al., Antimicrob. Agents Chemother. 44:1019-1028, 2000; H. Lau et al., Antimicrob. Agents Chemother. 45:187-195, 2001). Although many of the compounds in the library were more potent than trimethoprim, none had the degree of selectivity of trimethoprim for C. parvum versus human DHFR. Collectively, the results of these assays comprise the largest available database of lipophilic antifolates as potential anticryptosporidial agents. The compounds in the library were also tested as inhibitors of the proliferation of intracellular C. parvum oocysts in canine kidney epithelial cells cultured in folate-free medium containing thymidine (10 microM) and hypoxanthine (100 microM). After 72 h of drug exposure, the number of parasites inside the cells was quantitated by indirect immunofluorescence microscopy. Sixteen compounds had IC(50)s of <3 microM, and five of these had IC(50)s of <0.3 microM and thus were comparable in potency to trimetrexate. The finding that submicromolar concentrations of several of the compounds in the library could inhibit in vitro growth of C. parvum in host cells in the presence of thymidine (dThd) and hypoxanthine (Hx) suggests that lipophilic DHFR inhibitors, in combination with leucovorin, may find use in the treatment of intractable C. parvum infections.

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.

Epidemiology of Pneumocystis carinii pneumonia in an era of effective prophylaxis: the relative contribution of non-adherence and drug failure

OBJECTIVE

To determine the relative contribution of patient non-adherence, provider failure to prescribe prophylaxis, and drug failure to the continued occurrence of Pneumocystis carinii pneumonia (PCP), and to determine correlates of non-adherence.

DESIGN

Retrospective case-control study.

METHODS

Patients with confirmed or presumptive PCP from May 1995 to September 1997 who had at least 6 months of prior HIV care (cases) were compared to controls matched for initial CD4 cell count and date of initial HIV care.

RESULTS

The incidence of PCP declined by 85% in the 28 months of the study. Of the 118 cases of PCP identified, 59 (50%) were in HIV care for > 6 months prior to PCP diagnosis. In a multivariate logistic regression model, risk factors for PCP among patients in HIV care were patient non-adherence [odds ratio (OR), 12.4; 95% confidence interval (CI), 6.4-23.5], use of prophylaxis other than trimethoprim-sulfamethoxazole (OR, 27.0; 95% CI, 13.8-52.9), and absence of antiretroviral use (OR, 7.5; 95% CI, 4.5-12.5). Provider non-adherence occurred in one out of 59 cases (2%), and five out of 106 controls (5%). Of the patients who developed PCP on prophylaxis, 18 cases (30%) appeared due to drug failure; there were no cases of apparent drug failure among patients on trimethoprim-sulfamethoxazole. In multivariate analysis, non-adherence was more common among patients of non-white race, those with a history of injecting drug use, and those with active substance abuse or psychiatric illness.

CONCLUSIONS

Patient non-adherence was the most common reason for the occurrence of PCP among patients in HIV care; provider non-adherence was uncommon. Drug failure occurred only among patients on prophylaxis other than trimethoprim-sulfamethoxazole.

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.

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.

Synthesis and antiparasitic and antitumor activity of 2, 4-diamino-6-(arylmethyl)-5,6,7,8-tetrahydroquinazoline analogues of piritrexim

Nineteen previously undescribed 2,4-diamino-6-(arylmethyl)-5,6,7, 8-tetrahydroquinazolines (5a-m, 10-12) were synthesized as part of a larger effort to assess the therapeutic potential of lipophilic dihydrofolate reductase (DHFR) inhibitors against opportunistic infections of AIDS. Condensation of appropriately substituted (arylmethyl)triphenylphosphoranes with 4, 4-ethylenedioxycyclohexanone, followed by hydrogenation (H2/Pd-C) and acidolysis, yielded the corresponding 4-(arylmethyl)cyclohexanones, which were then condensed with cyanoguanidine to form the tetrahydroquinazolines. Three simple 2, 4-diamino-6-alkyl-5,6,7,8-tetrahydroquinazoline model compounds (9a-c) were also prepared in one step from commercially available 4-alkylcyclohexanones by this method. Enzyme inhibition assays against rat liver DHFR, Pneumocystis carinii DHFR, and the bifunctional DHFR-TS enzyme from Toxoplasma gondii were carried out, and the selectivity ratios IC50(rat)/IC50(P. carinii) and IC50(rat)/IC50(T. gondii) were compared. The three most potent inhibitors of P. carinii DHFR were the 2,5-dimethoxybenzyl (5j), 3, 4-dimethoxybenzyl (5k), and 3,4,5-trimethoxybenzyl (5l) analogues, with IC50 values of 0.057, 0.10, and 0.091 microM, respectively. The remaining compounds generally had IC50 values in the 0.1-1.0 microM range. However all the compounds were more potent against the rat liver enzyme than the P. carinii enzyme and thus were nonselective. The T. gondii enzyme was always more sensitive than the P. carinii enzyme, with most of the analogues giving IC50 values of 0.01-0.1 microM. Moderate 5-10-fold selectivity for T. gondii versus rat liver DHFR was observed with five compounds, the best combination of potency and selectivity being achieved with the 2-methoxybenzyl analogue 5d, which had an IC50 of 0.014 microM and a selectivity ratio of 8.6. One compound (5l) was tested for antiproliferative activity against P. carinii trophozoites in culture at a concentration of 10 microgram/mL and was found to completely suppress growth over 7 days. The suppressive effect of 5l was the same as that of trimethoprim (10 microgram/mL) + sulfamethoxazole (250 microgram/mL), a standard clinical combination for the treatment of P. carinii pneumonia in AIDS patients. Four compounds (5a,h,k,l) were tested against T. gondii tachyzoites in culture and were found to have a potency (IC50 = 0.1-0.5 microM) similar to that of pyrimethamine (IC50 = 0.69 microM), a standard clinical agent for the treatment of cerebral toxoplasmosis in AIDS patients. Compound 5h was also active against T. gondii infection in mice when given qdx8 by peritoneal injection at doses ranging from 62.5 (initial dose) to 25 mg/kg. Survival was prolonged to the same degree as with 25 mg/kg clindamycin, another widely used drug against toxoplasmosis. Three compounds (5j-l) were tested for antiproliferative activity against human tumor cells in culture. Among the 25 cell lines in the National Cancer Institute panel for which data were confirmed in two independent experiments, the IC50 for at least two of these compounds was <10 microM against 17 cell lines (68%) and in the 0. 1-1 microM range against 13 cell lines (52%). One compound (5j) had an IC50 of <0.01 microM against four of the cell lines. The activity profiles of 5k,l were generally similar to that of 5j except that there were no cells against which the IC50 was <0.01 microM.

Therapeutic strategies targeting proteins that regulate folate and reduced folate transport

Folate is an essential vitamin which acts as a precursor for cofactors that regulate a variety of biochemical reactions. Cellular uptake of endogenous folates as well as antifolate agents such as methotrexate may be regulated by two independent transport proteins, the folate receptor and the reduced folate carrier. This paper reviews the molecular and functional characteristics of these transport systems and potential therapeutic approaches exploiting these targets in the treatment of cancer. Understanding of the molecular basis and functional characteristics of the transport of endogenous folates and folate analogs via the folate receptor and the reduced folate carrier has led to the development of novel antifolate agents through rational drug design and targeted therapeutic approaches for tumors that express or lack the presence of these transport proteins. With this knowledge, new and selective treatment will become available to more effectively treat patients with a variety of malignancies.

Pneumonia in AIDS patients in the critical care unit

Despite advances in prophylaxis and the reduction of mortality and morbidity resulting from highly active antiretroviral therapy, neumocystis pneumonia remains a common problem in HIV-infected patients. There are many possible causes for the continued prevalence of this condition. This article examines the characteristics, and some of the complex causes of P. carinii pneumonia in AIDS patients.

The impact of high-risk patients on the results of clinical trials

The results of clinical trials may not reflect equally the experiences of all their individual participants. By modeling populations where patients have very diverse baseline risks of suffering an event of interest, it can be seen that very sick patients of high risk become the major determinants of how many events occur in the whole population, even though they may represent only a small minority. Human immunodeficiency virus-related trials and trials of magnesium in acute myocardial infarction are analyzed. When the benefit or toxicity from a treatment varies with the baseline risk of each patient, the treatment effect may be markedly different in populations with a different representation of high- and low-risk patients. The results of small clinical trials studying heterogeneous populations with binary outcomes depend on the sampling and outcomes of very few high risk participants. Conversely, mega-trials studying homogeneous populations would miss subgroups or individuals with diverse treatment responses. In both cases, aggregate trial results may be misleading for the care of many individuals.

A population pharmacokinetic model of trimethoprim in patients with pneumocystis pneumonia, made with parametric and nonparametric methods

A population pharmacokinetic model of intravenously and orally administered trimethoprim in patients with acquired immunodeficiency syndrome and Pneumocystis carinii pneumonia has been made using a parametric iterative two-stage Bayesian and a nonparametric expectation maximization computer program. When good information was present in the serum level data, both methods obtained similar results. With the nonparametric expectation maximization program, the median apparent rate constant for absorption (Ka) was 1.602 hr-1, median slope (Ks) of the relationship between creatinine clearance and elimination was 0.001168 hr-1, median apparent volume of distribution (Vs) was 1.058 l/kg, and median fraction of oral dose absorbed (Fa) was 0.955. These results permit dosage individualization adjusted to body weight and renal function to achieve chosen serum level peak and trough goals. Peak goals of 9 ug/ml and trough goals of 5 ug/ml appear reasonable for most patients in this population, and should permit most to complete an effective course of therapy with a reduced risk for treatment-terminating hematologic toxicity. However, therapeutic goals should always be selected based on each patient's apparent need for the drug and the risk of toxicity that is justifiably acceptable to obtain the expected benefits of the drug.

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.

Pneumocystis carinii pneumonia

Pneumocystis carinii pneumonia (PCP) remains an important complication of AIDS. Advances have been made in establishing the taxonomy of the organism but the life cycle of the organism and pathogenetic mechanisms of disease remain obscure. In HIV patients the incidence of PCP has decreased because of widespread use of prophylaxis and survival of those with PCP has improved with use of adjunctive corticosteroid therapy. Less toxic drug therapies are still needed as well as better noninvasive diagnostic techniques.

Drug treatment of HIV-related opportunistic infections

The AIDS epidemic has led to the emergence of several disease entities which in the pre-AIDS era were rare or seemingly innocuous. Experience of treating these diseases varies. In some instances, such as Pneumocystis carinii pneumonia, there is an abundance of published literature to direct our course of action. However, for many of these newly recognised diseases our treatment experience is limited. Furthermore, in many instances, well controlled trials evaluating treatment modalities in the AIDS population are lacking. We have identified 13 disease entities (P. carinii pneumonia, toxoplasmosis, cryptococcosis, histoplasmosis, Mycobacterium tuberculosis, Mycobacterium avium complex, cytomegalovirus, coccidioidomycosis, isosporiasis, candidosis, Kaposi's sarcoma, herpes simplex virus, and varicella zoster virus) and have reviewed the current literature with regard to their treatment.

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.