Brentuximab vedotin, an antibody-drug conjugate, in patients with CD30-positive haematologic malignancies and hepatic or renal impairment.

AIMS: Brentuximab vedotin, an antibody-drug conjugate (ADC), selectively delivers the microtubule-disrupting agent monomethyl auristatin E (MMAE) into CD30-expressing cells. The pharmacokinetics of brentuximab vedotin have been characterized in patients with CD30-positive haematologic malignancies. The primary objective of this phase 1 open label evaluation was to assess the pharmacokinetics of brentuximab vedotin in patients with hepatic or renal impairment. METHODS: Systemic exposures were evaluated following intravenous administration of 1.2 mg kg(-1) brentuximab vedotin in patients with CD30-positive haematologic malignancies and hepatic (n = 7) or renal (n = 10) impairment and compared with those of unimpaired patients (n = 8) who received 1.2 mg kg(-1) brentuximab vedotin in another arm of the study. RESULTS: For any hepatic impairment, the ratios of geometric means (90% confidence interval) for AUC(0,∞) were 0.67 (0.48, 0.93) for ADC and 2.29 (1.27, 4.12) for MMAE. Mild or moderate renal impairment caused no apparent change in ADC or MMAE exposures. Severe renal impairment (creatinine clearance <30 ml min(-1) ; n = 3) decreased ADC exposures (0.71 [0.54, 0.94]) and increased MMAE exposures (1.90 [0.85, 4.21]). No consistent pattern of specific adverse events was evident, but analysis of the safety data was confounded by the patients' poor baseline conditions. Five patients died due to adverse events considered unrelated to brentuximab vedotin. All had substantial comorbidities and most had poor baseline performance status. CONCLUSIONS: Hepatic impairment and severe renal impairment may cause decreases in brentuximab vedotin ADC exposures and increases in MMAE exposures.

Single-unit dominance after double-unit umbilical cord blood transplantation coincides with a specific CD8+ T-cell response against the nonengrafted unit.

We investigated the potential role of an immune reaction in mediating the dominant engraftment of 1 cord blood unit in 14 patients who received a double-unit cord blood transplantation (CBT). In 10 patients, dominant engraftment of a single donor unit emerged by day 28 after CBT. In 9 of these 10 patients, a significant subset of CD8(+) CD45RO(+/-)CCR7(-) T cells, present in peripheral blood mononuclear cells and derived from the engrafting cord blood unit, produced interferon-gamma (IFN-gamma) in response to the nonengrafting unit. No significant population of IFN-gamma-secreting cells was detectable when posttransplantation peripheral blood mononuclear cells were stimulated against cells from the engrafted unit (P < .001) or from a random human leukocyte antigen disparate third party (P = .003). Three patients maintained persistent mixed chimerism after CBT, and no significant IFN-gamma-secreting cells were detected after similar stimulations in these patients (P < .005). Our data provide the first direct evidence in human double-unit CBT recipients that immune rejection mediated by effector CD8(+) T cells developing after CBT from naive precursors is responsible for the failure of 1 unit to engraft. Future investigations based on these findings may result in strategies to predict a dominant unit and enhance graft-versus-leukemia effect.

Comparisons of CD8+ T cells specific for human immunodeficiency virus, hepatitis C virus, and cytomegalovirus reveal differences in frequency, immunodominance, phenotype, and interleukin-2 responsiveness.

To better understand the components of an effective immune response to human immunodeficiency virus (HIV), the CD8(+) T-cell responses to HIV, hepatitis C virus (HCV), and cytomegalovirus (CMV) were compared with regard to frequency, immunodominance, phenotype, and interleukin-2 (IL-2) responsiveness. Responses were examined in rare patients exhibiting durable immune-mediated control over HIV, termed long-term nonprogressors (LTNP) or elite controllers, and patients with progressive HIV infection (progressors). The magnitude of the virus-specific CD8(+) T-cell response targeting HIV, CMV, and HCV was not significantly different between LTNP and progressors, even though their capacity to proliferate to HIV antigens was preserved only in LTNP. In contrast to HIV-specific CD8(+) T-cell responses of LTNP, HLA B5701-restricted responses within CMV pp65 were rare and did not dominate the total CMV-specific response. Virus-specific CD8(+) T cells were predominantly CD27(+)45RO(+) for HIV and CD27(-)45RA(+) for CMV; however, these phenotypes were highly variable and heavily influenced by the degree of viremia. Although IL-2 induced significant expansions of CMV-specific CD8(+) T cells in LTNP and progressors by increasing both the numbers of cells entering the proliferating pool and the number of divisions, the proliferative capacity of a significant proportion of HIV-specific CD8(+) T cells was not restored with exogenous IL-2. These results suggest that immunodominance by HLA B5701-restricted cells is specific to HIV infection in LTNP and is not a feature of responses to other chronic viral infections. They also suggest that poor responsiveness to IL-2 is a property of HIV-specific CD8(+) T cells of progressors that is not shared with responses to other viruses over which immunologic control is maintained.

Generation of HIV-1-specific CD8+ cell responses following allogeneic hematopoietic cell transplantation.

This study tested whether donor-derived HIV-specific immune responses could be detected when viral replication was completely suppressed by the continuous administration of highly active antiretroviral therapy (HAART). A regimen of fludarabine and 200 cGy total body irradiation was followed by infusion of allogeneic donor peripheral blood cells and posttransplantation cyclosporine and mycophenolate mofetil. Viral load, lymphocyte counts, and HIV-1-specific CD8(+) cell immune responses were compared before and after hematopoietic cell transplantation (HCT). Uninterrupted administration of HAART was feasible during nonmyeloablative conditioning and after HCT. The HIV RNA remained undetectable and no HIV-associated infections were observed. CD8(+) T-cell responses targeting multiple epitopes were detected before HCT. After HCT a different pattern of donor-derived HIV-specific CTL responses emerged by day +80, presumably primed in vivo. We conclude that allogeneic HCT offers the unique ability to characterize de novo HIV-1-specific immune responses. This clinical trial was registered at ClinicalTrials.gov (identifier: NCT00112593).

Brentuximab Vedotin plus Chemotherapy in North American Subjects with Newly Diagnosed Stage III or IV Hodgkin Lymphoma.

PURPOSE: To evaluate safety and efficacy outcomes for subjects on the ECHELON-1 study treated in North America (NA). PATIENTS AND METHODS: ECHELON-1 is a global, open-label, randomized phase III study comparing doxorubicin, vinblastine, and dacarbazine in combination with brentuximab vedotin (A+AVD) versus ABVD (AVD + bleomycin) as first-line therapy in subjects with stage III or IV classical Hodgkin lymphoma (cHL; NCT01712490). Subjects were randomized 1:1 to receive A+AVD or ABVD intravenously on days 1 and 15 of each 28-day cycle for up to 6 cycles. RESULTS: The NA subgroup consisted of 497 subjects in the A+AVD (n = 250) and ABVD (n = 247) arms. Similar to the primary analysis based on the intent-to-treat population, the primary endpoint [modified progression-free survival (PFS) per independent review] demonstrated an improvement among subjects who received A+AVD compared with ABVD (HR = 0.60; P = 0.012). For PFS, the risk of progression or death was also reduced (HR = 0.50; P = 0.002). Subsequent anticancer therapies were lower in the A+AVD arm. Grade 3 or 4 adverse events (AEs) were more common, but there were fewer study discontinuations due to AEs in the A+AVD arm as compared with ABVD. Noted differences between arms included higher rates of febrile neutropenia (20% vs. 9%) and peripheral neuropathy (80% vs. 56%), but lower rates of pulmonary toxicity (3% vs. 10%) in subjects treated with A+AVD versus ABVD. CONCLUSIONS: The efficacy benefit and manageable toxicity profile observed in the NA subgroup of ECHELON-1 support A+AVD as a frontline treatment option for patients with stage III or IV cHL.

Multidrug-resistant Enterococcus faecium meningitis in a toddler: characterization of the organism and successful treatment with intraventricular daptomycin and intravenous tigecycline.

A case of enterococcal meningitis in a toddler is presented. The organism was highly resistant to all drugs previously used for pediatric Gram-positive meningitis. She was successfully treated with intraventricular and intravenous daptomycin and intravenous tigecycline. The organism was characterized as a member of CC17, a notorious emerging nosocomial clone of Enterococcus faecium.

Activation-induced expression of CD137 permits detection, isolation, and expansion of the full repertoire of CD8+ T cells responding to antigen without requiring knowledge of epitope specificities.

CD137 is a member of the TNFR-family with costimulatory function. Here we show that it also has many favorable characteristics as a surrogate marker for antigen-specific activation of human CD8(+) T cells. Although undetectable on unstimulated CD8(+) T cells, it is uniformly up-regulated 24 hours after stimulation on virtually all responding cells regardless of differentiation stage or profile of cytokine secretion, which circumvents limitations of current surrogate markers for defining the repertoire of responding cells based on only individual functions. Antibody-labeled responding CD137(+) cells can be easily and efficiently isolated by flow sorting or magnetic beads to substantially enrich antigen-specific T cells. To test this approach for epitope discovery, we examined in vitro priming of naive T cells from healthy donors to Wilms tumor antigen 1 (WT1), a protein overexpressed in various malignancies. Two overlapping pentadecamers were identified as immunogenic, and further analysis defined WT1((286-293)) as the minimal amino acid sequence and HLA-Cw07 as the HLA restriction element. In conclusion, this approach appears to be an efficient and sensitive in vitro technique to rapidly identify and isolate antigen-specific CD8(+) T cells present at low frequencies and displaying heterogeneous functional profiles, and does not require prior knowledge of the specific epitopes recognized or the HLA-restricting elements.

Immune evasion proteins of human cytomegalovirus do not prevent a diverse CD8+ cytotoxic T-cell response in natural infection.

Although cytomegalovirus (CMV) expresses proteins that interfere with antigen presentation by class I major histocompatibility complex (MHC) molecules, CD8+ cytotoxic T cells (CTLs) are indispensable for controlling infection and maintaining latency. Here, a cytokine flow cytometry assay that employs fibroblasts infected with a mutant strain of CMV (RV798), which is deleted of the 4 viral genes that are responsible for interfering with class I MHC presentation, was used to examine the frequency and specificity of the CD8+ CTLs to CMV in immunocompetent CMV-seropositive individuals. A large fraction of the CD8+ CTL response was found to be specific for viral antigens expressed during the immediate early and early phases of virus replication and presented by fibroblasts infected with RV798 but not wild-type CMV. These results demonstrate that the inhibition of class I antigen presentation observed in CMV-infected cells in vitro is not sufficient to prevent the induction of a broad repertoire of CD8+ CTLs after natural infection in vivo. Thus, reconstitution of T-cell immunity in immunodeficient patients by cell therapy or by vaccination may need to target multiple viral antigens to completely restore immunologic control of CMV.

Intracellular retention of the MHC class I-related chain B ligand of NKG2D by the human cytomegalovirus UL16 glycoprotein.

Infection by human CMV induces expression of the cellular MHC class I-related chain A (MICA) and chain B (MICB) surface proteins, which function as ligands for the activating NKG2D receptor. Engagement of NKG2D triggers NK cells and costimulates Ag-specific effector CD8 alphabeta T cells. The potency of MHC class I-related chain-NKG2D in stimulating these anti-viral immune responses may be countered by a CMV-encoded transmembrane glycoprotein, UL16, which specifically binds MICB as well as two of the UL16-binding proteins that are ligands of NKG2D. However, the function and significance of these interactions are undefined. Using a stably transfected B cell line, we show that expression of UL16 results in loss of surface MICB. This effect is caused by the failure of newly synthesized MICB to mature and transit the secretory pathway due to physical association with UL16. The intracellular retention of these protein complexes is mediated by a tyrosine-based motif in the cytoplasmic tail sequence of UL16, which determines localization to or retrieval from the trans-Golgi network. Deletion of this motif restores surface expression of MICB, whereas UL16 may be redirected to endosomal compartments. Predictably, the retention of MICB abrogates the stimulatory function of NKG2D. These results suggest a potential mechanism of viral immune evasion. However, this activity remains to be confirmed with CMV-infected fibroblasts or endothelial cells, in particular because MICB is normally coexpressed with MICA, which is not retained by UL16.

Telomere shortening in hematopoietic stem cell transplantation: a potential mechanism for late graft failure?

Telomeres serve to maintain the structural integrity of chromosomes, yet each somatic cell division is associated with a decrease in telomere length. The cumulative decrease in telomere length can impose an upper limit for the number of cell divisions that can occur before a cell senesces. When studied in vitro with fibroblasts, this limit is referred to as the Hayflick limit and usually occurs after 40 to 80 cell doublings. In theory, a similar replicative potential in a hematopoietic stem cell could support hematopoiesis in a person for more than 100 years. However, stem cells differentiate, and the telomere length differs among chromosomes within a single cell, among cell types, and among age-matched individuals. This variation in telomere length raises the possibility that long-term hematopoiesis by transplanted stem cells could, depending on the telomere length of the engrafted stem cell and the proliferative demand to which it is subjected, reach a Hayflick limit during the life span of the patient. Although significant shortening of telomeres is reported to occur within the first year posttransplantation, as yet no evidence has indicated that this shortening is associated with marrow function. In this review, we summarize reports on telomere shortening in stem cell transplantation recipients and report 2 cases in which graft failure is associated with significant telomere shortening.