Effect of oral semaglutide on energy intake, appetite, control of eating and gastric emptying in adults living with obesity: A randomized controlled trial.

AIM: To investigate the effects of once-daily oral semaglutide 50 mg on energy intake, appetite, control of eating and gastric emptying. METHODS: A clinical pharmacology, double-blind study was conducted in 61 adults with obesity randomized to once-daily oral semaglutide (dose-escalated to 50 mg) or placebo for 20 weeks. Energy intake was measured during an ad libitum lunch, and participant-reported appetite ratings and Control of Eating Questionnaire responses were assessed. Gastric emptying was measured using paracetamol absorption following a standardized breakfast. RESULTS: The relative change from baseline in ad libitum energy intake at week 20 (primary endpoint) was -39.2% points (95% confidence interval -59.0%, -19.4%) with semaglutide compared with placebo. Body weight was reduced by 9.8% with semaglutide and by 1.5% with placebo. Semaglutide reduced hunger, increased fullness and satiety, and was associated with fewer food cravings and better control of eating versus placebo. No statistically significant difference in gastric emptying was observed at week 20. CONCLUSIONS: In participants with obesity, once-daily oral semaglutide 50 mg reduced energy intake, body weight and appetite, and improved control of eating. There was no evidence of delayed gastric emptying at week 20, as measured through paracetamol absorption.

Midostaurin drug interaction profile: a comprehensive assessment of CYP3A, CYP2B6, and CYP2C8 drug substrates, and oral contraceptives in healthy participants.

PURPOSE: Midostaurin, approved for treating FLT-3-mutated acute myeloid leukemia and advanced systemic mastocytosis, is metabolized by cytochrome P450 (CYP) 3A4 to two major metabolites, and may inhibit and/or induce CYP3A, CYP2B6, and CYP2C8. Two studies investigated the impact of midostaurin on CYP substrate drugs and oral contraceptives in healthy participants. METHODS: Using sentinel dosing for participants' safety, the effects of midostaurin at steady state following 25-day (Study 1) or 24-day (Study 2) dosing with 50 mg twice daily were evaluated on CYP substrates, midazolam (CYP3A4), bupropion (CYP2B6), and pioglitazone (CYP2C8) in Study 1; and monophasic oral contraceptives (containing ethinylestradiol [EES] and levonorgestrel [LVG]) in Study 2. RESULTS: In Study 1, midostaurin resulted in a 10% increase in midazolam peak plasma concentrations (Cmax), and 3-4% decrease in total exposures (AUC). Bupropion showed a 55% decrease in Cmax and 48-49% decrease in AUCs. Pioglitazone showed a 10% decrease in Cmax and 6% decrease in AUC. In Study 2, midostaurin resulted in a 26% increase in Cmax and 7-10% increase in AUC of EES; and a 19% increase in Cmax and 29-42% increase in AUC of LVG. Midostaurin 50 mg twice daily for 28 days ensured that steady-state concentrations of midostaurin and the active metabolites were achieved by the time of CYP substrate drugs or oral contraceptive dosing. No safety concerns were reported. CONCLUSION: Midostaurin neither inhibits nor induces CYP3A4 and CYP2C8, and weakly induces CYP2B6. Midostaurin at steady state has no clinically relevant PK interaction on hormonal contraceptives. All treatments were well tolerated.

Combination of pasireotide and octreotide: effects on GH and IGF-I secretion and glucose metabolism in healthy volunteers.

PURPOSE: To assess the pharmacokinetics, pharmacodynamics and tolerability of different doses of octreotide and pasireotide (subcutaneous [sc] and long-acting release [LAR]) when co-administered in healthy volunteers. METHODS: This was an exploratory, Phase I, single-centre study. Healthy adults were enrolled in a staggered approach into seven cohorts to receive octreotide and pasireotide (sc and LAR formulations), alone or in combination. Plasma drug concentrations, growth hormone (GH), insulin-like growth factor I (IGF-I), and plasma glucose were assessed at baseline, immediately after sc treatment, and 21 and 28 days after LAR treatment. RESULTS: Of 88 enrolled subjects, 52 and 82 participated in sc and LAR dosing phases, respectively. There were no relevant pharmacokinetic interactions between octreotide and pasireotide. In combination, pasireotide sc (150 µg) and octreotide sc (100/300 µg) resulted in numerically greater reductions in insulin levels and a higher incidence of AEs than either single agent; the rapid (within 1 h) increase in plasma glucose after pasireotide was delayed with combination treatment. Octreotide sc and pasireotide sc, alone or in combination, reduced IGF-I levels and led to undetectable GH levels in most subjects. During the LAR phase, addition of a low dose of pasireotide (5 mg) to a standard dose of octreotide (20 mg) resulted in an ~2-fold reduction in median IGF-I versus octreotide 20 mg 21 days post-dose; this effect was numerically greater than seen for pasireotide 20 mg alone. Peak plasma glucose was substantially lower after LAR than sc dosing. Interestingly, glucose levels were also numerically lower in the pasireotide 5 mg plus octreotide 20 mg group than for 20 mg of octreotide or pasireotide alone. AEs were less frequent after LAR than sc dosing. CONCLUSIONS: Combined low doses of pasireotide LAR (5 mg) and octreotide LAR (10-30 mg) provided greater suppression of IGF-I than either single agent and did not increase blood glucose or incidence of AEs versus either agent alone.

Effect of oral semaglutide on the pharmacokinetics of thyroxine after dosing of levothyroxine and the influence of co-administered tablets on the pharmacokinetics of oral semaglutide in healthy subjects: an open-label, one-sequence crossover, single-center, multiple-dose, two-part trial.

BACKGROUND: Oral semaglutide comprises the glucagon-like peptide-1 analog, semaglutide, and sodium N-(8-[2-hydroxybenzoyl] amino) caprylate (SNAC). Levothyroxine has similar dosing conditions to oral semaglutide. This trial investigated if oral semaglutide co-administered with levothyroxine affects thyroxine (T4) exposure and if multiple placebo tablets co-administered with oral semaglutide affect semaglutide exposure. RESEARCH DESIGN AND METHODS: In this one-sequence crossover trial, 45 healthy subjects received levothyroxine (600 µg single-dose) alone, or with concomitant SNAC 300 mg or concomitant oral semaglutide 14 mg at steady-state. Subjects also received oral semaglutide 14 mg at steady-state alone or with five placebo tablets once-daily for 5 weeks. RESULTS: A 33% increase in total T4 exposure was observed with levothyroxine/oral semaglutide vs levothyroxine alone, but baseline-corrected maximum concentration (Cmax) was unaffected. SNAC alone did not affect total T4 exposure, whereas Cmax was slightly decreased. A 34% decrease in semaglutide exposure was observed when oral semaglutide was co-administered with placebo tablets, and Cmax also decreased. CONCLUSIONS: Levothyroxine pharmacokinetics were influenced by co-administration with oral semaglutide. Monitoring of thyroid parameters should be considered when treating patients with both oral semaglutide and levothyroxine. Oral semaglutide exposure was influenced by co-administration with multiple tablets, which is addressed in the dosing guidance.

Absence of QTc Prolongation with Sodium N-(8-[2-Hydroxybenzoyl] Amino) Caprylate (SNAC), an Absorption Enhancer Co-Formulated with the GLP-1 Analogue Semaglutide for Oral Administration.

INTRODUCTION: Oral delivery of proteins, including glucagon-like peptide 1 (GLP-1) receptor agonists, is impeded by low gastrointestinal permeation. Oral semaglutide has been developed for once-daily oral administration by co-formulation of the GLP-1 analogue semaglutide with an absorption enhancer, sodium N-(8-[2-hydroxybenzoyl] amino) caprylate (SNAC, 300 mg). A randomised, partially double-blind, placebo-controlled thorough QT/corrected QT (QTc) trial was conducted to confirm the absence of unacceptable QTc interval prolongation with SNAC. QT is defined as interval on the electrocardiogram, measured from the start of the QRS complex to the end of the T wave. METHODS: Part A of the study sought to identify an appropriate dose of SNAC (which was substantially higher than that used in the oral semaglutide co-formulation) for QTc assessment. Three sequential healthy volunteer cohorts were randomised to escalating single oral doses of SNAC (1.2, 2.4 or 3.6 g) or placebo. Following identification of an appropriate dose, a cross-over trial was conducted (Part B). Healthy volunteers received one of four treatment sequences, including single oral doses of SNAC, moxifloxacin (positive control) and placebo. Primary objectives were to (1) assess adverse events (AEs) with escalating SNAC doses and (2) confirm that SNAC does not cause unacceptable QTc interval prolongation versus placebo, using the Fridericia heart rate-corrected QT interval (QTcF). RESULTS: All subjects completed Part A (N = 36) and 46 subjects completed Part B. In Part A, all AEs were mild to moderate in severity; no relationship was identified between AE incidence and SNAC dose. SNAC 3.6 g, the maximum investigated SNAC dose, was selected for Part B. There was no unacceptable prolongation of the QTcF interval with SNAC 3.6 g, and assay sensitivity was demonstrated with moxifloxacin as the positive control. There was no significant exposure-response relationship between SNAC concentration and QTcF interval, and no instances of QTc interval > 450 ms or increases > 30 ms. CONCLUSION: This QT/QTc trial demonstrates that SNAC doses 12-fold higher than the 300 mg dose used in the oral formulation of semaglutide do not cause unacceptable prolongation of the QTcF interval. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT02911870.

Medications that are taken orally can be broken down by acid in the stomach before they are absorbed and therefore be less effective. Oral semaglutide is a novel type 2 diabetes medication that is formulated with the absorption enhancer sodium N-(8-[2-hydroxybenzoyl] amino) caprylate (SNAC), which helps to protect against semaglutide degradation in the stomach. Regulatory authority guidelines recommend that new therapies should be tested for prolongation of the QT interval, an important part of the heart's electrical cycle. A previous trial demonstrated that semaglutide alone, which is currently available as an injectable diabetes therapy, did not prolong the QT interval when given in doses higher than those used in patients. Therefore, the current trial was conducted to assess whether the SNAC component of oral semaglutide has any relevant prolonging effect on the QT interval. Following regulatory guidelines for trials evaluating prolongation of the QT interval, the first part of the trial aimed to find a suitably high dose of SNAC. The second part of the trial aimed to confirm that SNAC does not prolong the QT interval. The results of this trial demonstrated that a 3.6 g dose of SNAC, which is 12-fold higher than the amount contained in oral semaglutide, does not prolong the QT interval. The safety and tolerability of SNAC 1.2 g, 2.4 g and 3.6 g were assessed in this trial and no concerns were identified. These results, taken alongside those of the previous QT interval study with subcutaneous semaglutide, indicate no relevant effect of oral semaglutide on the QT interval.

Effect of Various Dosing Conditions on the Pharmacokinetics of Oral Semaglutide, a Human Glucagon-Like Peptide-1 Analogue in a Tablet Formulation.

INTRODUCTION: Oral semaglutide is a novel tablet formulation of the human glucagon-like peptide-1 analogue semaglutide. In two trials, the effects of prior food ingestion (food effect), post-dose fasting period and water volume with dosing (dosing conditions) on oral semaglutide pharmacokinetics were investigated. METHODS: Subjects received once-daily oral semaglutide for 10 days. In the food-effect trial, 78 healthy subjects were randomised 1:1:1 to fed (meal 30 min pre-dose; 240 mL water with dosing), fasting (overnight until 4 h post-dose; 240 mL) or reference (fasting overnight until 30 min post-dose; 120 mL) arms. In the dosing conditions trial, 161 healthy men were randomised into eight dosing groups (overnight fasted with 50/120 mL water and 15/30/60/120 min post-dose fasting). Semaglutide plasma concentrations were measured frequently until 504 h after the 10th dose. RESULTS: In the food-effect trial, limited or no measurable semaglutide exposure was observed in the fed arm, while all subjects in the fasting arm had measurable semaglutide exposure. Area under the semaglutide concentration-time curve (AUC0-24h,semaglutide,day10) and maximum semaglutide concentration (Cmax,semaglutide,day10) were numerically greater by approximately 40% for the fasting versus reference arm (p = 0.082 and p = 0.080, respectively). In the dosing conditions trial, AUC0-24h,semaglutide,day10 and Cmax,semaglutide,day10 were not different between water volumes (p = 0.541 and p = 0.676), but increased with longer post-dose fasting (p < 0.001). CONCLUSION: Administration of oral semaglutide in the fasting state with up to 120 mL water and at least 30 min post-dose fasting results in clinically relevant semaglutide exposure. These dosing conditions have been used in the oral semaglutide phase 3 trials and are part of the approved label. TRIAL REGISTRATION: ClinicalTrials.gov identifiers NCT02172313, NCT01572753.

Effect of Oral Semaglutide on the Pharmacokinetics of Levonorgestrel and Ethinylestradiol in Healthy Postmenopausal Women and Furosemide and Rosuvastatin in Healthy Subjects.

BACKGROUND: The first oral glucagon-like peptide-1 receptor agonist (GLP-1RA) comprises semaglutide co-formulated with the absorption enhancer, sodium N-(8-[2-hydroxybenzoyl] amino) caprylate (SNAC). Oral semaglutide may alter the pharmacokinetics of co-administered drugs via effects of semaglutide or SNAC. Two separate one-sequence crossover trials investigated the effects of oral semaglutide and SNAC on the pharmacokinetics of ethinylestradiol, levonorgestrel, furosemide and rosuvastatin. METHODS: Healthy, postmenopausal women (n = 25) received once-daily combined ethinylestradiol and levonorgestrel (Trial 1) and healthy male and female subjects (n = 41) received single doses of furosemide and rosuvastatin (Trial 2), either alone, with SNAC alone or with oral semaglutide. Lack of drug-drug interaction was concluded if 90% confidence intervals (CIs) for the ratio of area under the plasma concentration-time curve (AUC) or maximum concentration (Cmax), with/without oral semaglutide, were within a pre-specified interval (0.80-1.25). RESULTS: The AUC values of ethinylestradiol and levonorgestrel were not affected by oral semaglutide co-administration (estimated ratios [90% CI] 1.06 [1.01-1.10] and 1.06 [0.97-1.17], respectively); Cmax was not affected. The no-effect criterion was not met for furosemide or rosuvastatin for the AUC (1.28 [1.16-1.42] and 1.41 [1.24-1.60], respectively) or Cmax. SNAC alone did not affect the AUC or Cmax of ethinylestradiol, levonorgestrel or rosuvastatin; the Cmax of furosemide was slightly decreased. Adverse events were similar to those previously observed for GLP-1RAs (both trials). CONCLUSION: Co-administration with oral semaglutide did not affect the pharmacokinetics of ethinylestradiol or levonorgestrel. There was a small increase in exposure of furosemide and rosuvastatin; however, these increases are not expected to be of clinical relevance. CLINICAL TRIAL REGISTRATION NUMBERS: NCT02845219 and NCT03010475.

The effect of semaglutide 2.4 mg once weekly on energy intake, appetite, control of eating, and gastric emptying in adults with obesity.

AIM: To investigate the effects of once-weekly subcutaneous (s.c.) semaglutide 2.4 mg on gastric emptying, appetite, and energy intake in adults with obesity. MATERIALS AND METHODS: A double-blind, parallel-group trial was conducted in 72 adults with obesity, randomized to once-weekly s.c. semaglutide (dose-escalated to 2.4 mg) or placebo for 20 weeks. Gastric emptying was assessed using paracetamol absorption following a standardized breakfast. Participant-reported appetite ratings and Control of Eating Questionnaire (CoEQ) responses were assessed, and energy intake was measured during ad libitum lunch. RESULTS: The area under the concentration-time curve (AUC) for paracetamol 0 to 5 hours after a standardized meal (AUC0-5h,para ; primary endpoint) was increased by 8% (P = 0.005) with semaglutide 2.4 mg versus placebo at week 20 (non-significant when corrected for week 20 body weight; P = 0.12). No effect was seen on AUC0-1h,para , maximum observed paracetamol concentration, or time to maximum observed paracetamol concentration. Ad libitum energy intake was 35% lower with semaglutide versus placebo (1736 versus 2676 kJ; estimated treatment difference -940 kJ; P <0.0001). Semaglutide reduced hunger and prospective food consumption, and increased fullness and satiety when compared with placebo (all P <0.02). The CoEQ indicated better control of eating and fewer/weaker food cravings with semaglutide versus placebo (P <0.05). Body weight was reduced by 9.9% with semaglutide and 0.4% with placebo. Safety was consistent with the known profile of semaglutide. CONCLUSIONS: In adults with obesity, once-weekly s.c. semaglutide 2.4 mg suppressed appetite, improved control of eating, and reduced food cravings, ad libitum energy intake and body weight versus placebo. There was no evidence of delayed gastric emptying at week 20, assessed indirectly via paracetamol absorption.

A randomized study investigating the effect of omeprazole on the pharmacokinetics of oral semaglutide.

BACKGROUND: Since the first oral glucagon-like peptide-1 analog comprises semaglutide co-formulated with an absorption enhancer, sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, which induces a transient, localized increase in gastric pH, we have investigated whether a proton pump inhibitor affects the pharmacokinetics of oral semaglutide. RESEARCH DESIGN AND METHODS: A single-center, randomized, open-label, parallel-group trial investigated pharmacokinetic interactions of oral semaglutide with omeprazole (40 mg once-daily) in 54 healthy subjects. Primary endpoints were area under the plasma concentration-time curve over 24 h for semaglutide (AUC0-24h,semaglutide,Day10) and maximum concentration of semaglutide (Cmax,semaglutide,Day10) at day 10. RESULTS: Exposure of semaglutide appeared to be slightly increased, although not statistically significantly, with oral semaglutide plus omeprazole versus oral semaglutide alone (AUC0-24h,semaglutide,Day10 [estimated treatment ratio 1.13; 90%CI 0.88, 1.45] and Cmax,semaglutide,Day10 [estimated treatment ratio 1.16; 90%CI 0.90, 1.49]). Gastric pH was higher with oral semaglutide and omeprazole versus oral semaglutide alone. Adverse events were mild or moderate and, most commonly, gastrointestinal disorders. CONCLUSIONS: There was a slight non-statistically significant increase in semaglutide exposure when oral semaglutide was administered with omeprazole, but this is not considered clinically relevant and no dose adjustment is likely to be required.

Management of hyperglycemia associated with pasireotide (SOM230): healthy volunteer study.

AIMS: Pasireotide, a multireceptor-targeted somatostatin analogue with efficacy in Cushing's disease and acromegaly, can affect glucose metabolism due to inhibition of insulin secretion and incretin hormone responses. A study was therefore conducted to evaluate different antihyperglycemic drugs in the management of pasireotide-associated hyperglycemia. METHODS: This was a 1-week, Phase I, open-label study. Healthy male volunteers were randomized to pasireotide 600 µg sc bid alone or co-administered with metformin 500 mg po bid, nateglinide 60 mg po tid, vildagliptin 50mg po bid, or liraglutide 0.6 mg sc qd. An oral glucose tolerance test (OGTT) was performed on days 1 and 7 to evaluate effects on serum insulin, plasma glucose and glucagon levels. Safety/tolerability and pharmacokinetic effects were also evaluated. RESULTS: Ninety healthy male volunteers were enrolled (n=18 per arm). After 7 days of treatment, plasma glucose AUC post-OGTT increased by 69% with pasireotide alone. The effect was reduced by 13%, 29%, 45% and 72% with co-administration of metformin, nateglinide, vildagliptin and liraglutide, respectively. On day 7, compared with pasireotide alone, the decrease in serum insulin was attenuated with nateglinide, metformin, liraglutide and vildagliptin co-administration (levels were 3%, 6%, 34% and 71% higher, respectively). Minimal changes in plasma glucagon were observed. Adverse events were consistent with the safety profiles of the drugs used. CONCLUSIONS: Vildagliptin and liraglutide were most effective in minimizing pasireotide-associated hyperglycemia in healthy volunteers.

Effects of Subcutaneous Pasireotide on Cardiac Repolarization in Healthy Volunteers: a Single­Center, Phase I, Randomized, Four­Way Crossover Study.

The aim of this study was to evaluate the effects of subcutaneous pasireotide on cardiac repolarization in healthy volunteers. Healthy volunteers were randomized to one of four treatment sequences (n = 112) involving four successive treatments in different order: pasireotide 600 µg (therapeutic dose) or 1,950 µg (maximum tolerated dose) bid by subcutaneous injection (sc), placebo injection and oral moxifloxacin. Maximum ΔΔQTcI occurred 2 hours post-dose for both doses of pasireotide. Mean ΔΔQTcI was 13.2 milliseconds (90% CI: 11.4, 15.0) and 16.1 milliseconds (90% CI: 14.3, 17.9) for the 600 and 1,950 µg bid doses, respectively. Maximal placebo-subtracted change in QTcI from baseline for moxifloxacin was 11.1 (90% CI: 9.3, 12.9) milliseconds. Both pasireotide doses caused a reduction in heart rate: maximal heart rate change compared with placebo occurred at 1 hour for pasireotide 600 µg bid and at 0.5 hours for pasireotide 1,950 µg bid, with heart rate reductions of 10.4 and 14.9 bpm, respectively. At the therapeutic dose of 600 µg, pasireotide has a modest QT-prolonging effect. The relatively small increase of ∼3 milliseconds in ΔΔQTcI in the presence of a 3.25-fold increase in dose suggests a relatively flat dose­effect relationship of pasireotide on ΔΔQTcI in healthy volunteers. No safety concerns for pasireotide were identified during the study.

[Nephrogenic systemic fibrosis]. / Nephrogene systemische Fibrose.

The approval of gadofosveset trisodium as the first imaging agent for magnetic resonance angiography (MRA) by the US Food and Drug administration (FDA) in December 2008 served as a motive to review a rare serious adverse reaction possibly related to the use of gadolinium based contrast agents. Nephrogenic systemic fibrosis (NSF) is a disabling and potentially fatal disease characterized by thickening and hardening of the skin, especially of the extremities. It is restricted to patients with renal insufficiency (estimated glomerular filtration rate [eGFR] < 30ml/min/ 1,73 m2). Systemic manifestations may involve skeletal muscles, lungs and myocardium. Progressive fibrosis may restrict the movement of joints, leading to contractures limiting mobility of the patients. Since the first report by Cowper and co-workers in 2000 as "skleromyxedema-like cutaneous disease in renal-dialysis patients", hundreds of cases have been published. In 2006 a possible relationship to gadolinium based contrast agents used for magnetic resonance imaging was established, especially when applied in high doses, although the exact pathophysiologic mechanisms remain unclear. Gadolinium based contrast agents bind gadolinium (Gd3+) ions into a chelate complex (GBC). It has been proposed, that due to prolonged exposure in patients with renal insufficiency Gd3+ ions may increasingly be released from the chelate. There are several theories how these unbound Gd3+ ions may initiate fibrotic changes. Macrophages, that engulf these ions, may release profibrotic cytokines by which circulating fibrocytes are attracted to the tissue. Free Gd3+ ions may also activate tissue transglutaminase, which in turn activates transforming growth factor beta (TGF-beta) produced by dendritic cells. Active TGF-beta attracts further dendritic cells and on the other hand stimulates skin fibroblasts to produce extracellular matrix proteins (e.g. collagen), whereas matrix degrading enzymes are decreased. The chemical structures of the chelates account for different stabilities of the GBC agents. Most cases of NSF were reported after exposure to gadodiamide or gadopentetate dimeglumine, which represent linear, non-ionic imaging agents. In contrast, macrocyclic, ionic imaging agents have rarely been associated with this disease. Although the recently FDA approved gadofosveset trisodium has a linear structure and a long plasma half life due to high protein binding, there have been no reports of NSF up to date. This may be due to the much lower doses required for this agent compared to gadodiamide (approx. 0,03 mmol/l compared to 0,2 mmol/). Since there is no effective therapy for NSF, the top priority is to avoid exposure to gadolinium based contrast agents in patients at increased risk. In case of renal insufficiency (eGFR < 30 ml/min/1,73 m2) they should only be given if clearly necessary. After a thorough risk-benefit-assessment, the lowest possible dose should be used.

After major ABO-mismatched allogeneic hematopoietic progenitor cell transplantation, erythroid engraftment occurs later in patients with donor blood group A than donor blood group B.

BACKGROUND: Isohemagglutinins directed against the donor blood group frequently delay erythroid engraftment after major ABO-mismatched allogeneic hematopoietic progenitor cell transplantation (HPCT). Graft-versus-host reactions are capable of accelerating the clearance of isohemagglutinins. Whether immunogenicity of the A- and B-antigen is important in this process is unknown. PATIENTS AND METHODS: Data of 807 patients from three centers were screened for patients with major or bidirectionally ABO-mismatched donors. Clinical data and red blood cell (RBC) transfusion support were analyzed retrospectively. RESULTS: A total of 158 patients with major or bidirectionally mismatched donors were identified. After major mismatched HPCT, patients with anti-A directed against the donor blood group required RBC transfusion support for a median of 109 days (range, 0-324 days) compared to 21 days (range, 2-98 days) for patients with anti-B directed against donor blood group (log-rank test, p = 0.0001). Other risk factors associated with prolonged RBC transfusion support in univariate analysis were age (p = 0.024), cytomegalovirus infection (p = 0.016), hemolytic anemia (p = 0.027), and chronic bleeding disorders (p = 0.038). The independent influence of donor blood group and recipient age were confirmed in a multivariate analysis. CONCLUSION: These results indicate that the immunogenicity of the ABO antigen plays an important role for the kinetics of erythroid engraftment after ABO-mismatched HPCT.