Non-malignant Setting Research Articles

The Experiences and Views on Palliative Care of Older People with Multimorbidities, Their Family Caregivers and Professionals in a Spanish Hospital.

The increasing prevalence of complex chronic diseases in the population over 65 years of age is causing a major impact on health systems. This study aims to explore the needs and preferences of the multimorbid patient and carers to improve the palliative care received. The perspective of professionals who work with this profile of patients was also taken into account. A qualitative study was conducted using semi-structured interviews with open-ended questions. Separate topic guides were developed for patients, careers and health professionals. We included 12 patients, 11 caregivers and 16 health professionals in Spain. The results showed multiple unmet needs of patients and families/caregivers, including feelings of uncertainty, a sense of fear, low awareness and knowledge about palliative care in non-malignant settings, and a desire to improve physical, psychosocial and financial status. A consistent lack of specialized psychosocial care for both patients and caregivers was expressed and professionals highlighted the need for holistic needs assessment and effective and early referral pathways to palliative care. There is a lack of institutional support for multimorbid older patients in need of palliative care and important barriers need to be addressed by health systems to face the significant increase in these patients.

51. PS4 utilization for PIK3CA variants implicated in disorders of somatic mosaicism

The 2015 ACMG/AMP variant classification criteria have increased uniformity of variant interpretation. Efforts to refine their utility include consensus gene-disease specific variant interpretation guidelines and application refinements outlined by expert panels. Classification of somatic variation observed in a non-malignant setting is not addressed by the guidelines and is an area in need of such work. Our laboratory performs clinical testing for Disorders of Somatic Mosaicism (DoSM) and frequently encounters clinically significant PIK3CA variants of apparently somatic origin.

Chronic obstructive pulmonary disease and advance care planning: A synthesis of qualitative literature on patients' experiences.

Advance Care Planning supports patients to share their personal values, goals, and preferences for future medical care with their family members and healthcare professionals. The aim of this review was to uncover what is known about patients with Chronic Obstructive Pulmonary Disease and their experiences with Advance Care Planning. A systematic review and thematic synthesis of qualitative studies was undertaken. Five databases were searched for qualitative articles published between 2009-2019. The review was guided by the PRISMA framework and seven studies met the eligibility criteria. Thematic synthesis of descriptive themes in each article was undertaken to develop overarching analytical themes, related to the experience of patients with Chronic Obstructive Pulmonary Disease and Advance Care Planning. Four analytical themes emerged from the review of the articles that met the inclusion criteria: patient readiness and willingness for Advance Care Planning discussions; considering the future; trusted relationships with healthcare professionals; and shared decision making. Patients with Chronic Obstructive Pulmonary Disease are generally open to Advance Care Planning discussions with healthcare professionals who are well-informed, and trusted by the patient. Models of care that integrate Advance Care Planning are beneficial in other non-malignant settings, and may be a way forward to support Advance Care Planning as part of routine care for patients with Chronic Obstructive Pulmonary Disease.

Immune Reconstitution Following TCRαβ/CD19-Depleted Hematopoietic Cell Transplantation for Hematologic Malignancy in Pediatric Patients

TCRαβ/CD19-depleted HCT has been used with excellent outcomes in pediatric patients with hematologic malignancies, and several studies have demonstrated rapid immune reconstitution in the nonmalignant setting. However, immune recovery following TCRαβ/CD19-depleted hematopoietic cell transplantation (HCT) for malignancy remains incompletely elucidated. Furthermore, the majority of studies to date have used haploidentical and matched unrelated donors. Here we report results of immune reconstitution following TCRαβ/CD19-depleted HCT for hematologic malignancy in 51 pediatric patients with hematologic malignancies, the majority of whom received grafts from unrelated donors. Grafts were from matched unrelated (n = 20), mismatched unrelated (n = 20), and haploidentical (n = 11) donors. The median CD34+ cell dose was 10.2 × 106/kg (range, 4.54 to 20 × 106/kg), and the median TCRαβ+ cell dose was 2.53 × 104/kg (range, 0 to 44.9 × 104/kg). Conditioning was myeloablative with either busulfan or total body irradiation, cyclophosphamide, and thiotepa. Thirty-three patients also received rabbit antithymocyte globulin. No prophylactic post-transplantation immune suppression was routinely given. Forty-three patients received rituximab on day +1 for recipient positive Epstein-Barr virus serology.Forty-nine patients (96%) engrafted with a median time to neutrophil recovery of 13 days (range, 8 to 30 days). Thirty-seven patients (73%) are alive at a median follow-up of 25 months (range, 6 to 50 months). Nine patients (18%) developed grade II-IV acute graft-versus-host disease (GVHD), and 5 patients (11%) developed extensive chronic GVHD. Twenty-six patients (51%) experienced viral reactivation. T cell reconstitution was rapid with significant numbers of CD3+, CD4+, and CD8+ T cells present on first assessment at 4 months post-HCT, and significant numbers of naïve CD4+ T cells were present by 8 months post-HCT. Chronic GVHD was associated with delayed T cell recovery; however, T cell reconstitution was not affected by underlying diagnosis, donor source, TCRαβ+ T cell dose, conditioning regimen, or use of antithymocyte globulin. B cell recovery mirrored T cell recovery, and i.v. Ig was discontinued at a median of 8 months (range, 4 to 22 months) post-HCT in patients alive and relapse-free at last follow-up. Immune reconstitution is rapid following TCRαβ/CD19-depleted HCT in pediatric patients with hematologic malignancies. Donor graft source, haploidentical or unrelated, did not affect immune reconstitution. Viral reactivation is common in the first 100 days post-HCT, indicating that improved T cell defense is needed in the early post-HCT period.

A Single Dose of a Novel Anti-Human CD117-Amanitin Antibody Drug Conjugate (ADC) Engineered for a Short Half-Life Provides Dual Conditioning and Anti-Leukemic Activity and Extends Survival Compared to Standard of Care in Multiple Preclinical Models of Acute Myeloid Leukemia (AML)

Hematopoietic stem cell transplant (HSCT) can be a highly effective, and often curative, treatment for patients with AML. At present, myeloablative conditioning (MAC) regimens are associated with severe acute and long-term toxicities. A subset of transplant-eligible AML patients undergoes reduced-intensity conditioning (RIC) regimens; while reducing toxicities, RIC regimens have higher incidence of post-transplant relapse and graft failure vs MAC. Thus, the need for safe and effective targeted conditioning agents for a broader use in transplant in both malignant as well as non-malignant settings is critical. We developed MGTA-117, an anti-human CD117 (c-kit)-targeted antibody (Ab) engineered for a short-half life (t1/2) conjugated to amanitin, an RNA polymerase II inhibitor, to enable ADC clearance prior to HSCT. MGTA-117 has a t1/2 of 91 hours in humanized NSG (hNSG) mice compared to the parental wild type (WT) Ab with a t1/2 of 217 hours in human FCRN mice. Via optimization of the linker-toxin moiety, the maximum tolerated dose (MTD) in C57BL/6 mice was improved 17-fold compared to previous generations of the ADC. The antibody component specifically binds CD117, which is expressed on hematopoietic stem and progenitor cells (HSPC) and in ~80% of patient cells with AML and MDS (Gao et al. PLOS One. 2015). When conjugated to amanitin, this ADC robustly depletes both CD117+ HSPCs and leukemic blasts. This targeted and optimized approach not only broadens the therapeutic window across preclinical models, but also provides the dual benefit of effective conditioning for HSCT and reduction of target-expressing tumor cells. Previously we have shown MGTA-117 elicits potent cytotoxicity on both primary human CD34+ cells and a CD117+ AML cell line in vitro. In hNSG mice, a single dose (0.1 mg/kg) of MGTA-117 selectively depleted ≥95% human HSPCs (Figures 1A and B). To demonstrate anti-leukemic activity of MGTA-117, we studied it in multiple human leukemic xenograft murine models that mimic untreated and refractory AML, including both cell line derived (Kasumi-1, CD117-expressing leukemia cell line, in NSG mice) and patient derived (AML PDX 1: J000106134, treatment naïve AML PDX and AML PDX 2: J000106132, heavily pretreated relapsed refractory AML PDX in NSG-SGM3 mice) xenograft models. MGTA-117 was well-tolerated in all three AML xenograft models both as a single dose (1-10 mg/kg) and as a multi-dose (3 mg/kg QODx2) regimen. In the Kasumi-1 model (Figure 1C), MGTA-117, both as a single dose (3 & 10 mg/kg) and as a multi-dose (3 mg/kg QODx2), resulted in a 2.4-2.7-fold increase in median survival compared to vehicle (PBS), isotype-ADC, or standard of care (SOC) cytarabine (ARA-C, 30 mg/kg QDx5). Furthermore, a single dose of MGTA-117 significantly decreased peripheral tumor burden leading to delayed tumor growth resulting in a 2-3.3 fold and 1.3-1.8 fold increase in median survival in the treatment naïve AML PDX 1 and highly pretreated AML PDX 2 models (respectively) compared to vehicle, isotype-ADC and SOC. ARA-C treatment demonstrated a modest improvement in survival in both the AML PDX 1 (1.3 fold), AML PDX 2 (1.3 fold) models compared to control. These data demonstrate that MGTA-117 has potential to be a potent targeted conditioning and anti-leukemia agent. Together with prior reports demonstrating MGTA-117 as an effective conditioning agent in an animal model, this targeted ADC approach has the potential to improve HSCT outcomes in AML by reducing leukemic burden peri-transplant and may decrease the toxicities associated with current conditioning regimens. Disclosures Lanieri: Magenta Therapeutics: Current Employment. Lamothe:Magenta Therapeutics: Current Employment. Miske:Magenta Therapeutics: Current Employment. McDonough:Magenta Therapeutics: Current Employment. Sarma:Magenta Therapeutics: Ended employment in the past 24 months. Bhattarai:Magenta Therapeutics: Current Employment. Latimer:Magenta Therapeutics: Current Employment. Dushime:Magenta Therapeutics: Current Employment. Jain:Magenta Therapeutics: Current Employment. Palchaudhuri:Magenta Therapeutics: Current Employment. Knihtila:Magenta Therapeutics: Current Employment. Pearse:Magenta Therapeutics: Ended employment in the past 24 months. Proctor:Magenta Therapeutics: Current Employment. Boitano:Magenta Therapeutics: Ended employment in the past 24 months, Patents & Royalties. Cooke:Magenta Therapeutics: Ended employment in the past 24 months, Patents & Royalties. Davis:Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company.

Abstract 5516: Immunological effects of SYK inhibition using TAK659 in patients diagnosed with diffuse large B cell lymphoma

Abstract Targeted inhibition of the BCR signaling pathway is a therapeutic option for patients diagnosed with Diffuse Large B-cell Lymphoma (DLBCL) currently under clinical evaluation. Inhibition of the proximal BCR signaling kinase SYK has been shown to have direct cytotoxic effect on malignant B lymphocytes. Moreover, SYK protein also participates in immumomodulatory processes involving the inflammasome, Fcγ receptor and T cell responses in non-malignant settings. Herein we aimed to study the immunological effects of treatment with TAK659 in patients diagnosed with DLBCL. For that we longitudinally studied changes in immune cells subpopulations and cytokines in the peripheral blood of seven patients undergoing treatment with TAK659 (phase I, first in human clinical trial; NCT03123393). Patients received 100 mg of TAK659 orally once a day in 28-day cycles until disease progression, unacceptable toxicities, or withdrawal for other reasons (estimated median treatment duration 6 months). Peripheral blood was collected serially before and during treatment (after 1 week). The relative percentages of CD4 and CD8 T cells were not significantly modified. Interestingly, treatment with TAK659 significantly induced a reduction in regulatory T cells after 1 week. Additionally, treatment with TAK659 induced an increase in the proportion of central memory CD4 T cells after 1 week of treatment while effector memory went down, indicating a shift towards a more effector T cell profile. Regarding the expression of inhibitory receptors we observed a downregulation of PD-1 and LAG-3 in both CD4 and CD8 T cells after 1 week of treatment, as well as downregulation of CD4 and CD8 co-expressing PD-1 with LAG-3. Finally, we observed a reduction in the levels of IFN-γ in the plasma of patients after 1 week of treatment while TNF-α and IL-10 did not change. In order to assess if some of the immunological effects could be due to direct effect of TAK659 in T lymphocytes we treated PBMCs from healthy donors with increasing doses of TAK659 for 30' before 48 hours of TCR stimulation. The in vitro stimulation of T lymphocytes induced an increase in the proportion of regulatory T cells as well as induction of exhaustion markers in both CD4 and CD8 T cells that was counteracted by treatment with TAK659 that did not affect their viability. Overall, these findings provide initial evidence of the role of TAK 659 in potentiating the anti-tumoral immune response during treatment of DLBCL. Therefore, we believe that treatment with TAK659 can help to reinstall immune surveillance by exerting direct immunomodulatory effects which provides rationale for combination therapy not only in B-cell derived malignancies but also in solid tumors. Citation Format: Marta Crespo, Juan C. Nieto, Cristina Hernández, Cecilia del Carmen Carpio, Isabel Jiménez, Carlos Palacio, Júlia Carabia, Pau Abrisqueta, Francesc Bosch. Immunological effects of SYK inhibition using TAK659 in patients diagnosed with diffuse large B cell lymphoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5516.

A Clinician's Guide to Cancer-Derived Exosomes: Immune Interactions and Therapeutic Implications.

Understanding of the role of immunity in the regulation of cancer growth continues to rapidly increase. This is fuelled by the impressive results yielded in recent years by immune checkpoint inhibitors, which block regulatory pathways to increase immune-mediated cancer destruction. Exosomes are cell-secreted membranous nanoscale vesicles that play important roles in regulating physiological and pathophysiological processes. Cancer-derived exosomes (CDEXs) and their biologically-active cargos have been proven to have varied effects in malignant progression, including the promotion of angiogenesis, metastasis, and favorable microenvironment modification. More recently, there is an increasing appreciation of their role in immune evasion. In addition to CDEXs, there are immune-derived exosomes that facilitate communication between immune cells in the non-malignant setting. Investigation of cancer-mediated mechanisms behind interruption or modification of these normal exosomal pathways may provide further understanding of how malignant immune evasion is accomplished. Accumulating evidence indicates that immune-active CDEXs also have the potential to impact clinical oncological management. Whilst immune checkpoint inhibitors have well-established pharmacologically-targeted pathways involving the immune system, other widely used treatments such as radiation and cytotoxic chemotherapies do not. Thus, investigating exosomes in immunotherapy is important for the development of next-generation combination therapies. In this article, we review the ways in which CDEXs impact individual immune cell types and how this contributes to the development of immune evasion. We discuss the relevance of lymphocytes and myeloid-lineage cells in the control of malignancy. In addition, we highlight the ways that CDEXs and their immune effects can impact current cancer therapies and the resulting clinical implications.

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH): Optimal Management.

Hyponatremia, defined as serum sodium concentration <135 mEq/l, is the most common electrolyte balance disorder in clinical practice. Many causes are listed, but syndrome of inappropriate antidiuretic hormone secretion (SIADH) is certainly the most relevant, mainly in oncological and hospitalized patients. In this review, the pathophysiological and clinical aspects are described in detail. Patients’ extensive medical history and structured physical and biochemical tests are considered the milestones marking the way of the SIADH management as to provide early detection and proper correction. We focused our attention on the poor prognostic role and negative effect on patient’s quality of life of SIADH-induced hyponatremia in both malignant and non-malignant settings, stressing how optimal management of this electrolyte imbalance can result in improved outcomes and lower health costs.

A Non-Genotoxic Anti-CD117 Antibody Drug Conjugate (ADC) Designed for Patient Conditioning Prior to Stem Cell Transplant and HSC-Based Gene Therapy Has a Broad Therapeutic Window across Species

Current approaches to conditioning prior to transplant and gene therapy employ non-specific genotoxic agents that are associated with severe acute and long-term toxicities. Consequently, many transplant eligible patients either refuse transplant or receive reduced intensity regimens, which still have adverse toxicities with increased risk of relapse and graft failure. Importantly, patients with non-malignant disease may choose to forgo a potentially curative transplant due to risks of conditioning-associated toxicities, potentially limiting access of these patients to transplant and emerging HSC-based gene therapy. Thus, safe and effective targeted conditioning agents would have broad application to transplant in both malignant and non-malignant settings as well as gene therapy. We developed a CD117 antibody conjugated to amanitin (anti-CD117-AM) to specifically deplete hematopoietic stem and progenitor cells (HSPCs) as a novel approach to patient preparation for allogeneic and autologous transplant. ADCs have significant single agent anti-tumor activity in the clinic, however, achieving suitable tolerability at efficacious doses has presented a clinical challenge. We engineered the properties of the anti-CD117-AM to provide a broad therapeutic window across pre-clinical models. Through modification of the linker moiety, the maximum tolerated dose (MTD) of the ADC in C57Bl6 mice was improved 17-fold compared to previous versions. The engineered anti-CD117-AM maintained potent cytotoxicity on primary human CD34+ cells and a CD117+ AML cell line ( 95% of human HSPCs (Fig. 1A). Single doses of the anti-CD117-AM demonstrated robust tumor control in xenograft models of AML, despite its purposefully shortened half-life as a targeted agent for transplant indications (Fig. 1B). The tolerability of the engineered anti-CD117-AM was assessed in cynomolgus NHPs. The ADC was well-tolerated with an MTD at ≥ 2 mg/kg (Fig. 1C). A single dose of the ADC was able to drive marked depletion of HSPCs and downstream progeny. The pharmacokinetics of the ADC exhibited linear clearance supporting tolerability well above target saturation. In summary, optimization of the chemical linker between antibody and payload yielded a well-tolerated ADC with wide safety margins that could eliminate HSPCs and confer survival benefit in AML xenograft models. ADC-mediated conditioning through selective depletion of CD117+ cells may provide an improved approach to patient preparation for transplant in malignant and non-malignant disease including gene therapy, broadening patient access to potentially curative treatments.

Mean platelet volume and risk of thrombotic and bleeding complications in patients with Philadelphia chromosome negative myeloproliferative neoplasms.

: Philadelphia chromosome negative myeloproliferative neoplasms (MPNs) are associated with increased thrombosis and bleeding risk. Mean platelet volume (MPV) is associated with thrombosis in nonmalignant settings. This study evaluates the association between MPV and thrombosis and bleeding in MPN. Patients with MPN without prior thrombosis, nonhematologic malignancy or anticoagulant use were included in this retrospective analysis. The primary endpoint was arterial or venous thrombosis. The secondary endpoints were any bleeding and major bleeding. MPV was measured at diagnosis and during the index episode. A total of 135 MPN patients met the inclusion criteria. Over a median follow-up of 6.6 years, 23 patients (15.6%) experienced thrombosis. There was no difference in MPV at diagnosis (8.47 vs. 8.73 fl, P = 0.4) or during the index event between patients with or without thrombosis. Twelve patients (8.9%) had a bleeding event, whereas seven (5.2%) had major bleeding. MPV was significantly higher among patients with major bleeding, both at diagnosis (10.04 vs. 8.61, P = 0.005) and during the bleeding episode. There was no association after regression analysis of variables associated with MPV at diagnosis. MPV is not associated with thrombotic events in MPN. The study generates the hypothesis that MPV may be an indirect marker of bleeding in MPN.

British Society for Gene and Cell Therapy Annual Conference and Joint UK Regenerative Medicine Platform Meeting Royal Welsh College of Music & Drama Cardiff, Wales, United Kingdom Wednesday April 19-Friday April 21, 2017 Conference Abstracts.

British Society for Gene and Cell Therapy Annual Conference and Joint UK Regenerative Medicine Platform Meeting Royal Welsh College of Music & Drama Cardiff, Wales, United Kingdom Wednesday April 19-Friday April 21, 2017 Conference Abstracts.

The Conundrum of Genetic "Drivers" in Benign Conditions.

Advances in deep genomic sequencing have identified a spectrum of cancer-specific passenger and driver aberrations. Clones with driver anomalies are believed to be positively selected during carcinogenesis. Accumulating evidence, however, shows that genomic alterations, such as those in BRAF, RAS, EGFR, HER2, FGFR3, PIK3CA, TP53, CDKN2A, and NF1/2, all of which are considered hallmark drivers of specific cancers, can also be identified in benign and premalignant conditions, occasionally at frequencies higher than in their malignant counterparts. Targeting these genomic drivers can produce dramatic responses in advanced cancer, but the effects on their benign counterparts are less clear. This benign-malignant phenomenon is well illustrated in studies of BRAF V600E mutations, which are paradoxically more frequent in benign nevi (∼80%) than in dysplastic nevi (∼60%) or melanoma (∼40%-45%). Similarly, human epidermal growth factor receptor 2 is more commonly overexpressed in ductal carcinoma in situ (∼27%-56%) when compared with invasive breast cancer (∼11%-20%). FGFR3 mutations in bladder cancer also decrease with tumor grade (low-grade tumors, ∼61%; high-grade, ∼11%). “Driver” mutations also occur in nonmalignant settings: TP53 mutations in synovial tissue from rheumatoid arthritis and FGFR3 mutations in seborrheic keratosis. The latter observations suggest that the oncogenicity of these alterations may be tissue context–dependent. The conversion of benign conditions to premalignant disease may involve other genetic events and/or epigenetic reprogramming. Putative driver mutations can also be germline and associated with increased cancer risk (eg, germline RAS or TP53 alterations), but germline FGFR3 or NF2 abnormalities do not predispose to malignancy. We discuss the enigma of genetic “drivers” in benign and premalignant conditions and the implications for prevention strategies and theories of tumorigenesis.

P123 The Use of Indwelling Pleural Catheters For the Management of Non-Malignant Recurrent Pleural Effusions

Although indwelling pleural catheters (IPC) are commonly used to allow the outpatient management of malignant pleural effusions, an increasing number if IPCs are being inserted to control effusions caused by...

Acute graft‐versus‐host disease in pediatric allogeneic hematopoietic stem cell transplantation. Single‐center experience during 10 yr

a-GvHD may complicate allogeneic HSCT. In this retrospective single-center study, we evaluated incidence and risk factors of a-GvHD in 197 consecutive allogeneic pediatric HSCTs applying Glucksberg and NIH a-GvHD classifications. Among 179 eligible transplants, the cumulative incidence of grade 0-I a-GvHD was 48% and grade II-IV was 52%. None of the considered variables significantly influenced the incidence of grade II-IV a-GvHD. Malignancy and myeloablation were associated with an increased risk of classic a-GvHD (p < 0.01). Seventy-two percentage of children are alive, with a significant difference in OS and TRM between grade 0 and I vs. grade II and IV a-GvHD; this observation was reproduced in the non-malignant setting, while only a disparity in TRM was evidenced in children with malignancy. In our experience, the incidence of a-GvHD was similar, regardless of donor type. Myeloablation and malignant disease represented the only risk factors for classic a-GvHD. Our results highlight the need for a better prevention of this complication in the non-malignant setting.

Update on the role of palliative oxygen

Breathlessness remains a frequent and burdensome symptom for individuals with life-limiting symptoms in both malignant and nonmalignant settings. As oxygen therapy is frequently given as part of the management of breathlessness and is associated with costs, treatment burden and potential dangers, it is timely to review the efficacy and appropriateness of palliative oxygen therapy. Despite the widespread use of oxygen therapy in clinical and community settings, data supporting this approach is sparse. The benefits of long-term oxygen therapy for severely hypoxaemic people with chronic obstructive pulmonary disease are proven; however, mounting evidence suggests that oxygen does not confer additional benefit over medical air for the relief of refractory breathlessness in people with mild or absent hypoxaemia. On the basis of the findings of this review, the routine use of palliative oxygen therapy without detailed assessment of pathogenesis and reversibility of symptoms cannot be justified. Promoting self-management strategies, such as cool airflow across the face, exercise and psychological support for patients and carers, should be considered before defaulting to oxygen therapy. If palliative oxygen therapy is considered for individuals with transient or mild hypoxaemia, a therapeutic trial should be conducted with clinical review after 3 days to assess the net clinical benefit and patient preference.

Graft failure in allogeneic haematopoietic stem cell transplantation for non-malignant disorders: basics and perspectives

Graft failure is one of the major causes of morbidity and mortality after allogeneic haematopoietic stem cell transplantation, in particular for non-malignant disorders. Risk factors include HLA disparity, the use of T cell-depleted transplants, low doses of transplanted haematopoietic stem cells, viral infections, drug toxicity, and alloimmunisation due to inappropriate blood transfusions prior to transplantation. In patients at high risk for graft failure preventative strategies may include in vivo depletion of functioning host T cells and intensification of the post-transplant immunosuppressive treatment. Novel methods, such as depletion of only subsets of T cells or gene therapeutic graft engineering, may also prove to be useful in the non-malignant setting. The development of early mixed chimerism predisposes to subsequent graft failure, whereas specifically late mixed chimerism tends to be stable. In order to detect mixed chimerism as early as possible, chimerism studies should be performed close-meshed, especially in newly transplanted patients. In patients developing mixed chimerism, analysis of the T cell chimerism may reveal additional information of importance when making the appropriate therapeutic decision. Therapeutic options include modification of the immunosuppressive treatment, haematopoietic growth factors, donor lymphocyte infusions, application of booster doses of donor haematopoietic stem cells and second transplantation.