Targeting aberrant sialylation and fucosylation in prostate cancer cells using potent metabolic inhibitors.

Aberrant glycosylation is a hallmark of cancer and is not just a consequence, but also a driver of a malignant phenotype. In prostate cancer, changes in fucosylated and sialylated glycans are common and this has important implications for tumor progression, metastasis, and immune evasion. Glycans hold huge translational potential and new therapies targeting tumor-associated glycans are currently being tested in clinical trials for several tumor types. Inhibitors targeting fucosylation and sialylation have been developed and show promise for cancer treatment, but translational development is hampered by safety issues related to systemic adverse effects. Recently, potent metabolic inhibitors of sialylation and fucosylation were designed that reach higher effective concentrations within the cell, thereby rendering them useful tools to study sialylation and fucosylation as potential candidates for therapeutic testing. Here, we investigated the effects of global metabolic inhibitors of fucosylation and sialylation in the context of prostate cancer progression. We find that these inhibitors effectively shut down the synthesis of sialylated and fucosylated glycans to remodel the prostate cancer glycome with only minor apparent side effects on other glycan types. Our results demonstrate that treatment with inhibitors targeting fucosylation or sialylation decreases prostate cancer cell growth and downregulates the expression of genes and proteins important in the trajectory of disease progression. We anticipate our findings will lead to the broader use of metabolic inhibitors to explore the role of fucosylated and sialylated glycans in prostate tumor pathology and may pave the way for the development of new therapies for prostate cancer.

Sialic acid O-acetylation: From biosynthesis to roles in health and disease.

Sialic acids are nine-carbon sugars that frequently cap glycans at the cell surface in cells of vertebrates as well as cells of certain types of invertebrates and bacteria. The nine-carbon backbone of sialic acids can undergo extensive enzymatic modification in nature and O-acetylation at the C-4/7/8/9 position in particular is widely observed. In recent years, the detection and analysis of O-acetylated sialic acids have advanced, and sialic acid-specific O-acetyltransferases (SOATs) and O-acetylesterases (SIAEs) that add and remove O-acetyl groups, respectively, have been identified and characterized in mammalian cells, invertebrates, bacteria, and viruses. These advances now allow us to draw a more complete picture of the biosynthetic pathway of the diverse O-acetylated sialic acids to drive the generation of genetically and biochemically engineered model cell lines and organisms with altered expression of O-acetylated sialic acids for dissection of their roles in glycoprotein stability, development, and immune recognition, as well as discovery of novel functions. Furthermore, a growing number of studies associate sialic acid O-acetylation with cancer, autoimmunity, and infection, providing rationale for the development of selective probes and inhibitors of SOATs and SIAEs. Here, we discuss the current insights into the biosynthesis and biological functions of O-acetylated sialic acids and review the evidence linking this modification to disease. Furthermore, we discuss emerging strategies for the design, synthesis, and potential application of unnatural O-acetylated sialic acids and inhibitors of SOATs and SIAEs that may enable therapeutic targeting of this versatile sialic acid modification.

Prevalence and Impact of Fatigue in Children with Primary Immunodeficiency Disorders: a Quantitative Single-Center Study.

Although fatigue is a common symptom in adult patients with primary immunodeficiencies (PID), data in pediatric patients are limited. The goal of this study is to estimate the prevalence and impact of fatigue in children with PID as reported by patients, parents, and health-care providers. A retrospective single-center observational study was performed. Prevalence of fatigue was measured by reviewing medical charts of 54 children in our department who are on immunoglobulin replacement therapy. Both prevalence and impact were also measured by the PedsQL-Multidimensional Fatigue Scale (MFS) in 27 patients and 32 of their parents. This is an age-appropriate questionnaire for self-report of fatigue symptoms in patients aged 5-18 years and for parent proxy reports for patients aged 2-18 years. General, cognitive, and sleep-rest fatigue was measured, and a total fatigue score was calculated. Means, standard deviation and Z scores were calculated using age-specific reference values. Intraclass correlation coefficients (ICC) were calculated for comparison of scores provided by parents vs children's self-reported scores. Both chart review data and PedsQL-MFS showed fatigue rates of 65%. Pediatric PID patients of all ages had significantly lower scores on all subscales and total score of the PedsQL-MFS compared to healthy children, indicating greater perceived symptoms of fatigue. General fatigue was the most affected subscale in PID patients, suggesting that fatigue in these patients is mainly physical. Seventy-four percent of PID patients had a Z score lower than - 1 on the general fatigue subscale indicating severe fatigue. Child-parent concordance varied between 0.24 and 0.93. Our results show the feasibility of the PedsQL-MFS survey to evaluate the prevalence and severity of fatigue in children with PID and underscore the importance of this issue in our patient care.

A novel experimental approach for the selective isolation and characterization of human RNase MRP.

RNase MRP is a ribonucleoprotein complex involved in the endoribonucleolytic cleavage of different RNAs. Mutations in the RNA component of the RNP are the cause of cartilage hair hypoplasia. Patients with cartilage hair hypoplasia are characterized by skeletal dysplasia. Biochemical purification of RNase MRP is desired to be able to study its biochemical function, composition and activity in both healthy and disease situations. Due to the high similarity with RNase P, a method to specifically isolate the RNase MRP complex is currently lacking. By fusing a streptavidin-binding RNA aptamer, the S1m-aptamer, to the RNase MRP RNA we have been able to compare the relative expression levels of wildtype and mutant MRP RNAs. Moreover, we were able to isolate active RNase MRP complexes. We observed that mutant MRP RNAs are expressed at lower levels and have lower catalytic activity compared to the wildtype RNA. The observation that a single nucleotide substitution at position 40 in the P3 domain but not in other domains of RNase MRP RNA severely reduced the binding of the Rpp25 protein subunit confirmed that the P3 region harbours the main binding site for this protein. Altogether, this study shows that the RNA aptamer tagging approach can be used to identify RNase MRP substrates, but also to study the effect of mutations on MRP RNA expression levels and RNase MRP composition and endoribonuclease activity.

C-Reactive Protein, Procalcitonin, and White Blood Count to Rule Out Neonatal Early-onset Sepsis Within 36 Hours: A Secondary Analysis of the Neonatal Procalcitonin Intervention Study.

BACKGROUND: Neonatal early-onset sepsis (EOS) is one of the main causes of global neonatal mortality and morbidity, and initiation of early antibiotic treatment is key. However, antibiotics may be harmful. METHODS: We performed a secondary analysis of results from the Neonatal Procalcitonin Intervention Study, a prospective, multicenter, randomized, controlled intervention study. The primary outcome was the diagnostic accuracy of serial measurements of C-reactive protein (CRP), procalcitonin (PCT), and white blood count (WBC) within different time windows to rule out culture-positive EOS (proven sepsis). RESULTS: We analyzed 1678 neonates with 10 899 biomarker measurements (4654 CRP, 2047 PCT, and 4198 WBC) obtained within the first 48 hours after the start of antibiotic therapy due to suspected EOS. The areas under the curve (AUC) comparing no sepsis vs proven sepsis for maximum values of CRP, PCT, and WBC within 36 hours were 0.986, 0.921, and 0.360, respectively. The AUCs for CRP and PCT increased with extended time frames up to 36 hours, but there was no further difference between start to 36 hours vs start to 48 hours. Cutoff values at 16 mg/L for CRP and 2.8 ng/L for PCT provided a sensitivity of 100% for discriminating no sepsis vs proven sepsis. CONCLUSIONS: Normal serial CRP and PCT measurements within 36 hours after the start of empiric antibiotic therapy can exclude the presence of neonatal EOS with a high probability. The negative predictive values of CRP and PCT do not increase after 36 hours.

Cellular Fucosylation Inhibitors Based on Fluorinated Fucose-1-phosphates*.

Fucosylation of glycans impacts a myriad of physiological and pathological processes. Inhibition of fucose expression emerges as a potential therapeutic avenue for example in cancer, inflammation, and infection. In this study, we found that protected 2-fluorofucose 1-phosphate efficiently inhibits cellular fucosylation with a four to seven times higher potency than known inhibitor 2FF, independently of the anomeric stereochemistry. Nucleotide sugar analysis revealed that both the α- and ß-GDP-2FF anomers are formed inside the cell. In conclusion, we developed A2FF1P and B2FF1P as potent new tools for studying the role of fucosylation in health and disease and they are potential therapeutic candidates.

Cost impact of procalcitonin-guided decision making on duration of antibiotic therapy for suspected early-onset sepsis in neonates.

BACKGROUNDS: The large, international, randomized controlled NeoPInS trial showed that procalcitonin (PCT)-guided decision making was superior to standard care in reducing the duration of antibiotic therapy and hospitalization in neonates suspected of early-onset sepsis (EOS), without increased adverse events. This study aimed to perform a cost-minimization study of the NeoPInS trial, comparing health care costs of standard care and PCT-guided decision making based on the NeoPInS algorithm, and to analyze subgroups based on country, risk category and gestational age. METHODS: Data from the NeoPInS trial in neonates born after 34 weeks of gestational age with suspected EOS in the first 72 h of life requiring antibiotic therapy were used. We performed a cost-minimization study of health care costs, comparing standard care to PCT-guided decision making. RESULTS: In total, 1489 neonates were included in the study, of which 754 were treated according to PCT-guided decision making and 735 received standard care. Mean health care costs of PCT-guided decision making were not significantly different from costs of standard care (€3649 vs. €3616). Considering subgroups, we found a significant reduction in health care costs of PCT-guided decision making for risk category 'infection unlikely' and for gestational age ≥ 37 weeks in the Netherlands, Switzerland and the Czech Republic, and for gestational age < 37 weeks in the Czech Republic. CONCLUSIONS: Health care costs of PCT-guided decision making of term and late-preterm neonates with suspected EOS are not significantly different from costs of standard care. Significant cost reduction was found for risk category 'infection unlikely,' and is affected by both the price of PCT-testing and (prolonged) hospitalization due to SAEs.

Procalcitonin-guided decision making for duration of antibiotic therapy in neonates with suspected early-onset sepsis: a multicentre, randomised controlled trial (NeoPIns).

BACKGROUND: Up to 7% of term and late-preterm neonates in high-income countries receive antibiotics during the first 3 days of life because of suspected early-onset sepsis. The prevalence of culture-proven early-onset sepsis is 0·1% or less in high-income countries, suggesting substantial overtreatment. We assess whether procalcitonin-guided decision making for suspected early-onset sepsis can safely reduce the duration of antibiotic treatment. METHODS: We did this randomised controlled intervention trial in Dutch (n=11), Swiss (n=4), Canadian (n=2), and Czech (n=1) hospitals. Neonates of gestational age 34 weeks or older, with suspected early-onset sepsis requiring antibiotic treatment were stratified into four risk categories by their treating physicians and randomly assigned [1:1] using a computer-generated list stratified per centre to procalcitonin-guided decision making or standard care-based antibiotic treatment. Neonates who underwent surgery within the first week of life or had major congenital malformations that would have required hospital admission were excluded. Only principal investigators were masked for group assignment. Co-primary outcomes were non-inferiority for re-infection or death in the first month of life (margin 2·0%) and superiority for duration of antibiotic therapy. Intention-to-treat and per-protocol analyses were done. This trial was registered with ClinicalTrials.gov, number NCT00854932. FINDINGS: Between May 21, 2009, and Feb 14, 2015, we screened 2440 neonates with suspected early-onset sepsis. 622 infants were excluded due to lack of parental consent, 93 were ineligible for reasons unknown (68), congenital malformation (22), or surgery in the first week of life (3). 14 neonates were excluded as 100% data monitoring or retrieval was not feasible, and one neonate was excluded because their procalcitonin measurements could not be taken. 1710 neonates were enrolled and randomly assigned to either procalcitonin-guided therapy (n=866) or standard therapy (n=844). 1408 neonates underwent per-protocol analysis (745 in the procalcitonin group and 663 standard group). For the procalcitonin group, the duration of antibiotic therapy was reduced (intention to treat: 55·1 vs 65·0 h, p<0·0001; per protocol: 51·8 vs 64·0 h; p<0·0001). No sepsis-related deaths occurred, and 9 (<1%) of 1710 neonates had possible re-infection. The risk difference for non-inferiority was 0·1% (95% CI -4·6 to 4·8) in the intention-to-treat analysis (5 [0·6%] of 866 neonates in the procalcitonin group vs 4 [0·5%] of 844 neonates in the standard group) and 0·1% (-5·2 to 5·3) in the per-protocol analysis (5 [0·7%] of 745 neonates in the procalcitonin group vs 4 [0·6%] of 663 neonates in the standard group). INTERPRETATION: Procalcitonin-guided decision making was superior to standard care in reducing antibiotic therapy in neonates with suspected early-onset sepsis. Non-inferiority for re-infection or death could not be shown due to the low occurrence of re-infections and absence of study-related death. FUNDING: The Thrasher Foundation, the NutsOhra Foundation, the Sophia Foundation for Scientific research.

Prenatal counseling of an isolated fetal small head circumference during the second trimester expert ultrasound examination.

OBJECTIVE: To evaluate perinatal and postnatal outcomes of fetuses with an isolated small head circumference (HC) on expert ultrasound examination in the second trimester for further recommendations in prenatal care. STUDY DESIGN: In a retrospective cohort we included singleton-pregnancies with a fetal HC > -3.0 SD and ≤ -1.64 SD determined on expert ultrasound examination between 18 and 24 weeks of gestational age. Three subgroups were determined: "isolated small HC (ISHC)", "small HC plus abdominal circumference (AC) ≤ p10 (SHC+)" and "small HC plus AC ≤ p10 and Doppler abnormalities (SHC + D)". After ultrasound examination, genetic testing was sometimes offered and postnatally genetic tests were performed on indication. RESULTS: We included 252 pregnancies: 109 ISHC, 104 SHC+, and 39 SHC + D. In the ISHC and SHC+ subgroup, 96 % of the fetuses were born alive and did not die neonatal. In the SH + D group this was only 38 %. In the SHC+ subgroup, less fetuses were delivered vaginal (non-instrumental) compared to the ISHC subgroup (61 % vs. 73 %, p < 0.01). In the ISHC and SHC+ subgroup s some fetuses were diagnosed with congenital defects (4 % vs. 10 %, p = 0.08) and with a genetic anomaly (6.4 % vs. 7.7 %, p = 0.13) after 24 weeks or postnatally. In SHC + D subgroups 5 % presented with congenital defects and 2.6 % with a genetic anomaly. CONCLUSION: We conclude that fetuses with a small HC without structural anomalies on second trimester expert ultrasound require follow-up and special medical attention. We recommend differentiating between ISHC, SHC+, and SHC + D for prenatal counseling. Genetic testing and referral to a clinical geneticist should be considered.

Sialic acid blockade inhibits the metastatic spread of prostate cancer to bone.

BACKGROUND: Bone metastasis is a common consequence of advanced prostate cancer. Bisphosphonates can be used to manage symptoms, but there are currently no curative treatments available. Altered tumour cell glycosylation is a hallmark of cancer and is an important driver of a malignant phenotype. In prostate cancer, the sialyltransferase ST6GAL1 is upregulated, and studies show ST6GAL1-mediated aberrant sialylation of N-glycans promotes prostate tumour growth and disease progression. METHODS: Here, we monitor ST6GAL1 in tumour and serum samples from men with aggressive prostate cancer and using in vitro and in vivo models we investigate the role of ST6GAL1 in prostate cancer bone metastasis. FINDINGS: ST6GAL1 is upregulated in patients with prostate cancer with tumours that have spread to the bone and can promote prostate cancer bone metastasis in vivo. The mechanisms involved are multi-faceted and involve modification of the pre-metastatic niche towards bone resorption to promote the vicious cycle, promoting the development of M2 like macrophages, and the regulation of immunosuppressive sialoglycans. Furthermore, using syngeneic mouse models, we show that inhibiting sialylation can block the spread of prostate tumours to bone. INTERPRETATION: Our study identifies an important role for ST6GAL1 and α2-6 sialylated N-glycans in prostate cancer bone metastasis, provides proof-of-concept data to show that inhibiting sialylation can suppress the spread of prostate tumours to bone, and highlights sialic acid blockade as an exciting new strategy to develop new therapies for patients with advanced prostate cancer. FUNDING: Prostate Cancer Research and the Mark Foundation For Cancer Research, the Medical Research Council and Prostate Cancer UK.

Carriage of Mycoplasma pneumoniae in the upper respiratory tract of symptomatic and asymptomatic children: an observational study.

BACKGROUND: Mycoplasma pneumoniae is thought to be a common cause of respiratory tract infections (RTIs) in children. The diagnosis of M. pneumoniae RTIs currently relies on serological methods and/or the detection of bacterial DNA in the upper respiratory tract (URT). It is conceivable, however, that these diagnostic methods also yield positive results if M. pneumoniae is carried asymptomatically in the URT. Positive results from these tests may therefore not always be indicative of a symptomatic infection. The existence of asymptomatic carriage of M. pneumoniae has not been established. We hypothesized that asymptomatic carriage in children exists and investigated whether colonization and symptomatic infection could be differentiated by current diagnostic methods. METHODS AND FINDINGS: This study was conducted at the Erasmus MC-Sophia Children's Hospital and the after-hours General Practitioners Cooperative in Rotterdam, The Netherlands. Asymptomatic children (n = 405) and children with RTI symptoms (n = 321) aged 3 mo to 16 y were enrolled in a cross-sectional study from July 1, 2008, to November 30, 2011. Clinical data, pharyngeal and nasopharyngeal specimens, and serum samples were collected. The primary objective was to differentiate between colonization and symptomatic infection with M. pneumoniae by current diagnostic methods, especially real-time PCR. M. pneumoniae DNA was detected in 21.2% (95% CI 17.2%-25.2%) of the asymptomatic children and in 16.2% (95% CI 12.2%-20.2%) of the symptomatic children (p = 0.11). Neither serology nor quantitative PCR nor culture differentiated asymptomatic carriage from infection. A total of 202 children were tested for the presence of other bacterial and viral pathogens. Two or more pathogens were found in 56% (63/112) of the asymptomatic children and in 55.5% (50/90) of the symptomatic children. Finally, longitudinal sampling showed persistence of M. pneumoniae in the URT for up to 4 mo. Fifteen of the 21 asymptomatic children with M. pneumoniae and 19 of the 22 symptomatic children with M. pneumoniae in this longitudinal follow-up tested negative after 1 mo. CONCLUSIONS: Although our study has limitations, such as a single study site and limited sample size, our data indicate that the presence of M. pneumoniae in the URT is common in asymptomatic children. The current diagnostic tests for M. pneumoniae are unable to differentiate between asymptomatic carriage and symptomatic infection.

Engineering the sialome of mammalian cells with sialic acid mimetics.

Mammalian glycans show a diversity in sialic acid capping, constituting the sialome. Sialic acids can be extensively modified chemically, yielding sialic acid mimetics (SAMs). Here, we present a protocol for detecting and quantifying incorporative SAMs using microscopy and flow cytometry, respectively. We detail steps for linking SAMS to proteins with western blotting. Lastly, we detail procedures for incorporative or inhibitory SAMs and how SAMs can be used for the on-cell synthesis of high-affinity Siglec ligands. For complete details on the use and execution of this protocol, please refer to Büll et al.1 and Moons et al.2.

Anti-Cytosolic 5'-Nucleotidase 1A Autoantibodies Are Absent in Juvenile Dermatomyositis.

OBJECTIVE: To assess anti-cytosolic 5'-nucleotidase 1A (anti-cN-1A) autoantibodies in children with juvenile dermatomyositis (DM) and healthy controls, using 3 different methods of antibody detection, as well as verification of the results in an independent cohort. METHODS: Anti-cN-1A reactivity was assessed in 34 Dutch juvenile DM patients and 20 healthy juvenile controls using the following methods: a commercially available full-length cN-1A enzyme-linked immunosorbent assay (ELISA), a synthetic peptide ELISA, and immunoblotting with a lysate from cN-1A-expressing HEK 293 cells. Sera from juvenile DM patients with active disease and those with disease in remission were analyzed. An independent British cohort of 110 juvenile DM patients and 43 healthy juvenile controls was assessed using an in-house full-length cN-1A ELISA. RESULTS: Anti-cN-1A reactivity was not present in sera from juvenile DM patients or healthy controls when tested with the commercially available full-length cN-1A ELISA or by immunoblotting, in either active disease or disease in remission. Additionally, in the British juvenile DM cohort, anti-cN-1A reactivity was not detected. Three Dutch juvenile DM patients had weakly positive results for 1 of 3 synthetic cN-1A peptides measured by ELISA. CONCLUSION: Juvenile DM patients and young healthy individuals did not show anti-cN-1A reactivity as assessed by different antibody detection techniques.

Pharmacokinetics, pharmacodynamics, efficacy, and safety of a new recombinant asparaginase preparation in children with previously untreated acute lymphoblastic leukemia: a randomized phase 2 clinical trial.

The pharmacokinetics, pharmacodynamics, efficacy, and safety of a new recombinant Escherichia coli-asparaginase preparation was compared with Asparaginase medac. Thirty-two children with acute lymphoblastic leukemia were randomized to receive one of both agents at a dose of 5000 U/m(2) every 3 days, for a total of 8 doses during induction treatment. The serum activity-time profile after the first dose of recombinant asparaginase was similar to that of Asparaginase medac. The trough serum activities were greater than the desired threshold of 100 U/L in both treatment groups. Asparagine was completely depleted in serum and in cerebrospinal fluid, whereas glutamine levels were only moderately influenced. No significant difference between the 2 treatments regarding the degree of asparagine depletion, duration of depletion, complete remission rate, and minimal residual disease status at the end of induction, overall frequency or intensity of adverse events was seen. Observed adverse reactions are known as possible and labeled side effects of asparaginase treatment and chemotherapy. We conclude that the new recombinant asparaginase and other native Asparaginase medac are bioequivalent and have the same pharmacodynamic effects and the same direct toxicity profile in children with acute lymphoblastic leukemia. This trial was registered at http://www.controlled-trials.com as no. ISRCTN 75734403.

Pharmacokinetics, Short-term Safety and Efficacy of the Approved Once-daily Darunavir/Ritonavir Dosing Regimen in HIV-infected Children.

In this multicenter pharmacokinetic study in HIV-infected children (6-12 years of age), we validated the approved once-daily darunavir/ritonavir dosing recommendations. The geometric mean darunavir area under the plasma concentration-time curve was 63.1 h·mg/L, substantially lower than the mean value observed in adults. However, all trough levels were adequate, and short-term virologic outcome was good. These data support the use of the darunavir/ritonavir once-daily dosing recommendations.

Studies into the mechanism of measles-associated immune suppression during a measles outbreak in the Netherlands.

Measles causes a transient immune suppression, leading to increased susceptibility to opportunistic infections. In experimentally infected non-human primates (NHPs) measles virus (MV) infects and depletes pre-existing memory lymphocytes, causing immune amnesia. A measles outbreak in the Dutch Orthodox Protestant community provided a unique opportunity to study the pathogenesis of measles immune suppression in unvaccinated children. In peripheral blood mononuclear cells (PBMC) of prodromal measles patients, we detected MV-infected memory CD4+ and CD8+ T cells and naive and memory B cells at similar levels as those observed in NHPs. In paired PBMC collected before and after measles we found reduced frequencies of circulating memory B cells and increased frequencies of regulatory T cells and transitional B cells after measles. These data support our immune amnesia hypothesis and offer an explanation for the previously observed long-term effects of measles on host resistance. This study emphasises the importance of maintaining high measles vaccination coverage.

Perspectives of adolescents on decision making about participation in a biobank study: a pilot study.

OBJECTIVES: To be able to truly involve adolescents in decision making about clinical research participation, we need more insight in the perspective of adolescents themselves. To this end, adolescents in an ongoing biobank study were consulted to test a tentative decision assessment tool. METHODS: The perspectives of adolescents (n=8) concerning participation in decision making for research participation were explored in interviews with a tentative tool, which covered six topics: information material usage, understanding, disease perceptions, anxiety, decision-making process and role sharing. RESULTS: All adolescents unequivocally expressed the desire to be involved in decision making, but also wanted advice from their parents. The extent of the preferred role of adolescent versus parents varied between individuals. In decision making, adolescents relied on parents for information. More than half hardly used the information material. CONCLUSIONS: Adolescents in our study preferred a shared decision-making process. The extent of sharing varied between individuals. The decision assessment tool was a fruitful starting point to discuss adolescents' perspectives and may aid in tailoring the situation to the individual to achieve optimal participation practices. IMPLICATIONS: Consulting adolescents about their preferences concerning decision making using the tool will facilitate tailoring of the shared decision-making process and optimising the developing autonomy of minors.

Sustained Viral Suppression in HIV-infected Children on Once-daily Lopinavir/Ritonavir in Clinical Practice.

BACKGROUND: The use of lopinavir/ritonavir once-daily (LPV/r QD) has not been approved for children. Good short-term clinical, virologic and immunologic outcomes have been observed in children on LPV/r QD. METHODS: We evaluated the long-term effectiveness of a LPV/r QD containing regimen in HIV-1-infected children in clinical practice. Selected children (0-18 years of age) with an undetectable HIV-1 RNA viral load (<50 copies/mL) for at least 6 months on a twice-daily LPV/r-containing regimen switched to LPV/r QD. The main outcome measures were the percentage of patients with an undetectable HIV-1 viral load each subsequent year after switch to LPV/r QD (on treatment and last observation carried forward), and virologic failure during follow-up (>400 copies/mL twice within 6 months). Also, the exposure to LPV on the initial once-daily dosing regimen was determined. RESULTS: Forty children (median age: 6.5 years; range: 1.0-17) were included. Median follow-up was 6.3 years (range: 1.0-10.3). During yearly follow-up, the percentage of children with an undetectable viral load varied between 82% and 100% (on treatment) and 83% and 93% (last observation carried forward). Five children (12.5%) met the criteria for failure. CD4+ and CD8+ counts remained stable at normal values. Geometric mean LPV area under the plasma concentration-time curve (linear up-log down method) over a dosing interval from time 0 to 24 hours after dosing was 169.3 mg x h/L, and last observed drug concentration was 1.35 mg/L. Adverse events were encountered in 8 patients, were mainly gastrointestinal, and in these cases, no reason to stop treatment. CONCLUSION: A once-daily LPV/r-containing regimen in HIV-1-infected children with intensive clinical and therapeutic drug monitoring is well tolerated and has good long-term clinical, virologic and immunologic outcomes.