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Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome (WS) is a combined immunodeficiency caused by gain-of-function mutations in the C-X-C chemokine receptor type 4 (CXCR4) gene. We characterize a unique international cohort of 66 patients, including 57 (86%) cases previously unreported, with variable clinical phenotypes. Of 17 distinct CXCR4 genetic variants within our cohort, 11 were novel pathogenic variants affecting 15 individuals (23%). All variants affect the same CXCR4 region and impair CXCR4 internalization resulting in hyperactive signaling. The median age of diagnosis in our cohort (5.5 years) indicates WHIM syndrome can commonly present in childhood, although some patients are not diagnosed until adulthood. The prevalence and mean age of recognition and/or onset of clinical manifestations within our cohort were infections 88%/1.6 years, neutropenia 98%/3.8 years, lymphopenia 88%/5.0 years, and warts 40%/12.1 years. However, we report greater prevalence and variety of autoimmune complications of WHIM syndrome (21.2%) than reported previously. Patients with versus without family history of WHIM syndrome were diagnosed earlier (22%, average age 1.3 years versus 78%, average age 5 years, respectively). Patients with a family history of WHIM syndrome also received earlier treatment, experienced less hospitalization, and had less end-organ damage. This observation reinforces previous reports that early treatment for WHIM syndrome improves outcomes. Only one patient died; death was attributed to complications of hematopoietic stem cell transplantation. The variable expressivity of WHIM syndrome in pediatric patients delays their diagnosis and therapy. Early-onset bacterial infections with severe neutropenia and/or lymphopenia should prompt genetic testing for WHIM syndrome, even in the absence of warts.

Acquired aplastic anaemia is a rare, serious, immunologically mediated bone marrow failure syndrome, characterised by marrow hypoplasia of varying severity and significant pancytopenia. Careful attention and investigation, including molecular testing, is required to confirm the diagnosis and exclude other mimicking conditions, such as inherited bone marrow failure syndromes. In a proportion of patients, the disease evolves to myelodysplasia or acute myeloid leukaemia and in some there is an association with paroxysmal nocturnal haemoglobinuria. The disease has a major impact on patient quality of life. Haemopoietic stem/progenitor cell transplantation for eligible patients with an available donor is the only current curative therapy. Other patients may receive immunosuppression, most commonly with anti-thymocyte globulin and cyclosporin. An initial response to immunosuppression is often encouraging, but relapse is common. Supportive care, including management of transfusion requirements and infections, is central to management. Promising new diagnostic tools and emerging therapies will likely transform approaches to this important, chronic and life-threatening condition.

Background: WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome is a rare, autosomal-dominant primary immunodeficiency. Gain-of-function (GOF) mutations in the CXCR4 gene are the most common cause of WHIM syndrome, manifesting as panleukopenia with severe neutropenia, lymphopenia, and monocytopenia, recurrent bacterial infections, unusual susceptibility to human papillomavirus infections with intractable mucocutaneous warts, and increased risk of malignancy (McDermott DH, et al. Immunol Rev. 2019;2878:91-102). Mavorixafor is an investigational, small-molecule, selective antagonist of the CXCR4 receptor being developed as an oral, once-daily (QD) treatment for patients with WHIM syndrome (Dale DC, et al. Blood. 2020;136(26):2994-3003). Objective: We present an update on the clinical outcomes of patients with WHIM syndrome who continued in the long-term extension of the phase 2 study, highlighting long-term safety and efficacy. Methods: A long-term extension is ongoing as part of the open-label, prospective, dose-escalation, phase 2 study evaluating the safety and efficacy of mavorixafor (NCT03005327) in adults with WHIM syndrome. Individuals with a pathogenic GOF CXCR4 mutation and absolute neutrophil count ≤400/μL and/or absolute lymphocyte count ≤650/μL were included. All provided written informed consent. The primary objectives were to evaluate safety and tolerability and assess safe dosage. Exploratory efficacy end points included changes in infection rates, number of cutaneous warts, and white blood cell counts, compared to baseline. Researchers completed detailed interviews of 4 participants continuing in the study to assess their overall study experience and perceived treatment effects. Results: Five of 8 patients in the dose-finding phase 2 study entered into the long-term extension (LTE); median treatment duration was 148.4 weeks. One patient left the LTE because of study fatigue, and all 5 patients had dose escalation to 400 mg oral QD as of May 2021. As of the November 2020 data cutoff, annualized infection rates decreased from 5.6/year at study baseline to 2.2/year at 40 months' treatment, providing evidence of persistent reduction of infections over time. At doses of 300 and 400mg QD (n=7), the mean time above threshold for ANC and ALC were 12.7 hours (SD ± 9.8) and 16.9 hours (SD ± 5.9) compared to 2.1 hours (SD ± 3.3) and 11.5 hours (SD ± 5.9) at doses ≤200 mg QD, respectively. One patient experienced a 79% reduction in warts. Safety data review at May 2021 showed that there were 12 minor treatment-emergent adverse events (grade 1) with long-term treatment (46 months), no treatment-related infections of grade 3 or higher, no treatment-related serious adverse events, and no clinically significant laboratory abnormalities with mavorixafor treatment. Patient interviews revealed that all 4 LTE participants experienced good tolerability of mavorixafor and decreased frequency, severity, and duration of infections and decreased hospital/doctor visits. Three of 4 participants reported previous need for prophylactic treatment to prevent infection of minor wounds, but with mavorixafor, minor wounds healed without infection or need for prophylaxis. The mechanism of action of mavorixafor was of interest to 3 of 4 participants, who found it important that treatment address the underlying cause of disease, not simply the symptoms. Two participants reported a QOL improvement, and the other 2 reported that WHIM syndrome never affected their QOL Conclusion: Ongoing long-term treatment of adults with WHIM syndrome with mavorixafor 300 to 400mg shows durable increase in neutrophils and lymphocytes and sustained improvements in infections and warts. Detailed patient interviews for patient global impression of changes are consistent with sustained clinical benefit of long-term treatment. Mavorixafor has the potential to be a safe, effective, and long-term therapy targeting the underlying cause of WHIM syndrome. A global phase 3 registrational study is ongoing. Disclosures Dale: X4 Pharmaceuticals: Consultancy, Honoraria, Research Funding. Firkin: X4 Pharmaceuticals: Research Funding. Bolyard: X4 Pharmaceuticals: Research Funding. Tang: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Jiang: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. MacLeod: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Cadavid: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Hu: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company.

Acquired aplastic anaemia is a rare, serious, immunologically mediated bone marrow failure syndrome, characterised by marrow hypoplasia of varying severity and significant pancytopenia. Careful attention and investigation, including molecular testing, is required to confirm the diagnosis and exclude other mimicking conditions, such as inherited bone marrow failure syndromes. In a proportion of patients, the disease evolves to myelodysplasia or acute myeloid leukaemia and in some there is an association with paroxysmal nocturnal haemoglobinuria. The disease has a major impact on patient quality of life. Haemopoietic stem/progenitor cell transplantation for eligible patients with an available donor is the only current curative therapy. Other patients may receive immunosuppression, most commonly with anti-thymocyte globulin and cyclosporin. An initial response to immunosuppression is often encouraging, but relapse is common. Supportive care, including management of transfusion requirements and infections, is central to management. Promising new diagnostic tools and emerging therapies will likely transform approaches to this important, chronic and life-threatening condition.

Objective To determine the potential for arsenic trioxide (ATO) to be safely and effectively incorporated into induction therapy of newly diagnosed acute promyelocytic leukaemia (APL) in patients with severe chronic renal failure (CRF) by reduction of the ATO dosage to compensate for reduced renal elimination of arsenic in CRF. Patients and methods Two of the four CRF patients with APL in the study were dialysis-dependent, and two had eGFRs of 18 and 19 mL/min/1.73 m2. ATO dosage schedules were adjusted to obtain comparable whole-blood arsenic levels to those in APL patients with normal renal function who achieved molecular remission (MR) while receiving 10 mg ATO daily for 28 d. Results Average ATO administered per day in CRF patients ranged from 36 to 50% of the ATO administered to APL patients with normal renal function. No clinically significant cardiac, hepatic or other toxicities were detected. RT-PCR-negative MR was achieved after one treatment course in two patients and after two courses in the others. Relapse-free survival is 155, 60, 43 and 5 months. Conclusion The observations in this pilot study have demonstrated whole-blood arsenic levels can provide a guide to adjustments of ATO dosage schedules that permit safe and effective therapeutic outcomes in APL patients with severely compromised renal function.

Experience in the treatment of patients with acute promyelocytic leukaemia (APL) and accelerated phase chronic myeloid leukaemia with orally administered arsenic trioxide (ATO) in our institution since 1999 has demonstrated that bioavailability of oral ATO is comparable with intravenous administration, and similar outcomes are produced in treatment of APL. Oral administration was well tolerated, with good compliance, in patients not requiring hospitalisation for postinduction treatment and was particularly convenient for patients living considerable distances from our institution. Orally administered ATO can be considered a practicable option in management of APL.

Background: WHIM (Warts, Hypogammaglobulinemia, Infections, Myelokathexis) Syndrome is a serious, ultrarare genetic disorder caused by a gain-of-function mutation in CXCR4 that causes profound neutropenia and lymphopenia associated with increased rates of bacterial and viral infections. Long-term sequelae include hearing loss, bronchiectasis, and HPV-associated malignancies. The cancer risk in WHIM patients is estimated at 30% by age 40. There is currently no treatment that addresses the underlying mechanism of disease. G-CSF increases neutrophil counts but does not appear to reduce infection rates; use of parenteral gamma globulin has had mixed reports of benefit, but no controlled trials have been reported; Plerixafor, a CXCR4 antagonist, has been shown to increase leukocyte counts and reduce infection rates when absolute neutrophil counts (ANC)>600 mm-3 and absolute lymphocyte counts (ALC)>1000 mm-3, but is a parenteral agent that must be administered twice daily. X4P-001 is an orally available, allosteric inhibitor of CXCR4 that is being developed to treat WHIM. We report here the PK/PD data from the Phase 2 portion of Phase 2/3 trial X4P-001 MKKA (NCT03005327) in WHIM patients that led to selection of the dose for Phase 3 development. Methods: Study X4P-001 MKKA is a Phase 2/3 study. The primary objective of Ph2 portion was to assess the dose required to achieve a consistent increase in circulating neutrophils and lymphocytes. Adult patients with WHIM syndrome, with documented WHIM-associated genotype, and either ANC Results: Eight patients were enrolled and were evaluable for efficacy. 6 of 8 were female, and the mean (SD) age was 35.5 (13.37). Two patients started treatment with 50 mg, then received, 100, 150, 300 and 400 mg; 2 started at 100 and then received 200 and 300 mg; 2 started at 200 mg; 1 escalated to 300 and 400 mg while the other terminated after 1 week due to an adverse event (AE). Two started at 300 mg and did not escalate. Doses of at least 300 mg/day were needed to achieve success criteria for ANC, while at doses ≥100 mg/day, 50-100% met success criteria for ALC. (Figure 1) Two patients discontinued: 1 due to an AE of grade 1 rash, and 1 voluntarily withdrew. No serious AEs were reported. One patient had unrelated cholecystitis (grade 3). All other AEs were grade 1 or 2. Conclusions: Treatment of WHIM patients with X4P-001 results in meaningful increases in ANC at doses ≥300 mg, and in ALC at doses ≥100 mg per day for at least 5 weeks. These doses are anticipated to be associated with clinically meaningful outcomes in terms of infections and warts. X4P-001 appeared to be safe and well-tolerated at doses of 50-400 mg per day.4 Disclosures Dale: Athelas, Inc.: Equity Ownership; Amgen: Consultancy, Research Funding; Sanofi-Aventi: Consultancy, Honoraria; Cellerant: Other: Scientific Advisory Board; Hospira: Consultancy; Prolong: Consultancy; Beheringer-Ingelheim: Consultancy; Coherus: Consultancy. Hartmann:Cetara: Employment; X4P Pharmaceuticals: Consultancy. Brown:Certara: Employment; X4P Pharmaceuticals: Consultancy. Ebrahim:X4Pharmaceuticals: Employment. Gorelick:X4 Pharma: Consultancy; PIN Pharma: Consultancy; Shire: Consultancy; NGN Capital: Consultancy, Other: Venture partner; IntraBio: Consultancy; Zymo Consulting Group LLC: Employment.

Protein kinase C-beta II (PKC-beta II) expression has been reported to indicate inferior prognosis in diffuse large B-cell lymphoma (DLBCL) treated with anthracycline-based chemotherapy. This study compared prognostic significance of immunohistochemically determined PKC-beta II expression in de novo DLBCL treated with cyclophosphamide, doxorubicin, vincristine and prednisolone (CHOP) chemotherapy with and without rituximab. Outcomes were assessed in 80 consecutive patients, 48 treated with CHOP, and 32 with rituximab plus CHOP (R-CHOP). PKC-beta II expression correlated with inferior overall survival (OS) and progression-free survival (PFS) in CHOP-treated patients with low-risk International Prognostic Index (IPI) disease (0-2 adverse factors), but not in the overall patient group unstratified by IPI. PKC-beta II expression correlated with inferior OS and PFS in R-CHOP-treated patients unstratified by IPI status. Immunohistochemically demonstrated PKC-beta II expression thus identified patient subgroups where alternative treatment strategies may confer superior outcome. We now report that PKC-beta II expression has prognostic significance not only for CHOP therapy in low-risk IPI disease, but also for all patients receiving CHOP plus rituximab.

Summary Background Initial treatment of acute promyelocytic leukaemia traditionally involves tretinoin (all-trans retinoic acid) combined with anthracycline-based risk-adapted chemotherapy, with arsenic trioxide being the treatment of choice at relapse. To try to reduce the relapse rate, we combined arsenic trioxide with tretinoin and idarubicin in induction therapy, and used arsenic trioxide with tretinoin as consolidation therapy. Methods Patients with previously untreated genetically confirmed acute promyelocytic leukaemia were eligible for this study. Eligibilty also required Eastern Cooperative Oncology Group performance status 0–3, age older than 1 year, normal left ventricular ejection fraction, Q-Tc interval less than 500 ms, absence of serious comorbidity, and written informed consent. Patients with genetic variants of acute promyelocytic leukaemia (fusion of genes other than PML with RARA ) were ineligible. Induction comprised 45 mg/m 2 oral tretinoin in four divided doses daily on days 1–36, 6–12 mg/m 2 intravenous idarubicin on days 2, 4, 6, and 8, adjusted for age, and 0·15 mg/kg intravenous arsenic trioxide once daily on days 9–36. Supportive therapy included blood products for protocol-specified haemostatic targets, and 1 mg/kg prednisone daily as prophylaxis against differentiation syndrome. Two consolidation cycles with tretinoin and arsenic trioxide were followed by maintenance therapy with oral tretinoin, 6-mercaptopurine, and methotrexate for 2 years. The primary endpoints of the study were freedom from relapse and early death (within 36 days of treatment start) and we assessed improvement compared with the 2 year interim results. To assess durability of remission we compared the primary endpoints and disease-free and overall survival at 5 years in APML4 with the 2 year interim APML4 data and the APML3 treatment protocol that excluded arsenic trioxide. This study is registered with the Australian New Zealand Clinical Trials Registry, number ACTRN12605000070639. Findings 124 patients were enrolled between Nov 10, 2004, and Sept 23, 2009, with data cutoff of March 15, 2012. Four (3%) patients died early. After a median follow-up of 4·2 years (IQR, 3·2–5·2), the 5 year freedom from relapse was 95% (95% CI 89–98), disease-free survival was 95% (89–98), event-free survival was 90% (83–94), and overall survival was 94% (89–97). The comparison with APML3 data showed that hazard ratios were 0·23 (95% CI 0·08–0·64, p=0·002) for freedom from relapse, 0·21 (0·07–0·59, p=0·001) for disease-free survival, 0·34 (0·16–0·69, p=0·002) for event-free survival, and 0·35 (0·14–0·91, p=0·02) for overall survival. Interpretation Incorporation of arsenic trioxide in initial therapy induction and consolidation for acute promyelocytic leukaemia reduced the risk of relapse when compared with historical controls. This improvement, together with a non-significant reduction in early deaths and absence of deaths in remission, translated into better event-free and overall survival. Funding Phebra.

The characteristics of severe neutropenia with a delayed onset following administration of rituximab have been evaluated in 53 consecutively treated patients. All but one patient received rituximab for the treatment of non-Hodgkin's lymphoma. Eight episodes of grade 4 neutropenia were detected between 1 and 5 months after rituximab, when administered alone on five occasions, and on three occasions in combination with chemotherapy, where neutrophil counts had recovered prior to the development of neutropenia. In three episodes, the patients presented with sepsis. Development of neutropenia did not correlate with either the presence of detectable disease or the administration of further treatment. Neutropenia was associated with selective depletion of neutrophil precursors in all but one episode, where it was associated with generalized bone marrow hypoplasia. All episodes developed after a period of either normal or mildly depressed neutrophil counts following treatment with rituximab, and persisted for between several days and several months, before undergoing spontaneous recovery in four instances, and after administration of filgrastim in the remainder. Episodes of neutropenia were associated with disordered immune status manifested by lymphopenia and hypogammaglobulinaemia, raising the possibility that either disturbance of the balance of lymphocyte subsets or an immune dyscrasia induced by rituximab resulted in the development of this type of neutropenia.

Summary The risk of deep vein thrombosis and pulmonary embolism increases during, and for several weeks after, flights of four or more hours. Venous stasis due to prolonged immobility and obstruction to venous return from the legs is believed to accentuate any inherent predisposition of the traveller to venous thromboembolism. The incidence increases with flight duration, oestrogen ingestion, a prior episode of venous thromboembolism and coexisting medical or surgical conditions associated with increased risk. Clinically evident episodes occur at an incidence of about one per 4500 long-haul flights. The incidence increases in patients with other risk factors for thromboembolism, so prophylaxis with low molecular weight heparin can be considered. In people at low risk the adverse effects of prophylaxis outweigh the potential benefits.

Patients with suspected multiple myeloma should be investigated with screening tests. They may have a paraprotein in the serum, Bence-Jones protein in the urine, or both.

Hypercalcemia is an important complication in multiple myeloma as well as T-cell leukemia/lymphoma, and is moderately common in high and intermediate grade non-Hodgkin's lymphoma. The underlying mechanism has been unclear because the neoplastic cells are usually present in the bone marrow, where they are in a position to produce short range effects on bone resorption which are difficult to identify. This contrasts with the situation in hypercalcemia associated with non-metastatic carcinoma, where it has been clearly demonstrated that the most common cause is release from the tumor of a humoral mediator, Parathyroid Hormone-related Protein (PTHrP). Roles have been advocated in multiple myeloma for release of a number of other cytokines with osteolytic capacity on the basis of their enhancement of osteolytic activity in cultured fetal rat bone, although a causal relationship in patients has not been established. PTHrP has more recently been implicated in the genesis of hypercalcemia in patients with hematological malignancies by the demonstration in a proportion of cases of increased circulating levels of PTHrP, comparable to those in hypercalcemia due to cancer. Immunohistochemical studies indicate neoplastic hemopoietic cells can contain PTHrP, and thus have the capacity to act in a paracrine manner to enhance local bone resorption and contribute to the development of hypercalcemia.

September 2013; 54(9): 1864–1866© 2013 Informa UK, Ltd.ISSN: 1042-8194 print / 1029-2403 onlineDOI: 10.3109/10428194.2013.790967 Correspondence: Frank Firkin, Department of Medicine, St Vincent ’ s Hospital, Fitzroy, Victoria 3065, Australia. Tel: 613-9228-2574. Fax: 613-9288-2581. E-mail: ffi rkin@bigpond.net.au

Thirty-five patients (eight de novo, 27 relapsed disease) with low-grade non-Hodgkin's lymphoma (diffuse small lymphocytic, follicular small cleaved cell, follicular mixed cell, and lymphoplasmacytoid) were treated with 2-chlorodeoxyadenosine (2CdA) at a daily dose of 0.14 mg/kg for 5d (2 h infusion) for an average of three cycles. Minor treatment delays, generally due to haematological toxicities, occurred in nine of 105 cycles. Major toxicities were lymphopenia, neutropenia and thrombocytopenia. Opportunistic infections occurred in seven patients. Overall response rate was 69% (five complete, 19 partial) reaching 88% for de novo patients (two complete, five partial). Elevated beta 2-microglobulin level was negatively predictive of response (P = 0.0014). Eight of 24 responders relapsed, with a median follow-up of 13 months. 2CdA administered as an intermittent infusion shows considerable single-agent activity in low-grade lymphomas achieving high response rates of prolonged duration. Consideration of schedules where 2CdA is alternatively administered with combination chemotherapy appears warranted.

The treatment of acute promyelocytic leukemia has improved considerably after recognition of the effectiveness of all-trans-retinoic acid (ATRA), anthracycline-based chemotherapy, and arsenic trioxide (ATO). Here we report the use of all 3 agents in combination in an APML4 phase 2 protocol. For induction, ATO was superimposed on an ATRA and idarubicin backbone, with scheduling designed to exploit antileukemic synergy while minimizing cardiotoxicity and the severity of differentiation syndrome. Consolidation comprised 2 cycles of ATRA and ATO without chemotherapy, followed by 2 years of maintenance with ATRA, oral methotrexate, and 6-mercaptopurine. Of 124 evaluable patients, there were 4 (3.2%) early deaths, 118 (95%) hematologic complete remissions, and all 112 patients who commenced consolidation attained molecular complete remission. The 2-year rate for freedom from relapse is 97.5%, failure-free survival 88.1%, and overall survival 93.2%. These outcomes were not influenced by FLT3 mutation status, whereas failure-free survival was correlated with Sanz risk stratification (P[trend] = .03). Compared with our previously reported ATRA/idarubicin-based protocol (APML3), APML4 patients had statistically significantly improved freedom from relapse (P = .006) and failure-free survival (P = .01). In conclusion, the use of ATO in both induction and consolidation achieved excellent outcomes despite a substantial reduction in anthracycline exposure. This trial was registered at the Australian New Zealand Clinical Trials Registry (www.anzctr.org.au) as ACTRN12605000070639.

PURPOSE To compare complete response rates, time to failure, survival, and toxicity for patients with intermediate-grade non-Hodgkin's lymphoma (NHL) treated with cyclophosphamide, doxorubicin, vincristine, and prednisolone (CHOP) versus those treated with a regimen consisting of methotrexate, doxorubicin, cyclophosphamide, vincristine, prednisolone, and bleomycin (MACOP-B), in a multicenter, randomized controlled trial performed by 22 centers of the Australian and New Zealand Lymphoma Group (ANZLG). PATIENTS AND METHODS Between October 1986 and June 1991, 304 patients were randomized, of whom 236 were eligible for analysis. Eligibility criteria included diffuse small cleaved-cell, diffuse mixed small- and large-cell, follicular large-cell, diffuse large-cell, and large-cell immunoblastic, stages I bulky or II to IV. RESULTS There was no significant difference in complete response rates (51% for MACOP-B v 59% for CHOP), failure-free survival, or overall survival in the two treatment arms. The rate of death of MACOP-B patients relative to CHOP patients was estimated to be 0.91 (P = .64) when stratified by prognostic group. There were no significant differences between the two regimens in any of the prognostic subgroups. Toxicity was significantly more severe with MACOP-B, particularly cutaneous toxicity, stomatitis, and gastrointestinal ulceration. The average relative dose-intensity (RDI) of MACOP-B was 0.91 and of CHOP was 0.90, indicating good dose delivery in this multicenter group setting. CONCLUSION CHOP chemotherapy produced results equivalent to those of MACOP-B in patients with intermediate-grade NHL and with significantly fewer toxic complications. Despite relatively poor results in some patient subgroups, CHOP remains the standard chemotherapy for this disease, against which all new regimens should be compared.

The response of hemopoietic activity in long term culture of human bone marrow (LTMC) to exogenous c-kit ligand has been investigated. Addition of c-kit ligand as recombinant Stem Cell Factor after the adherent stromal cell layer had become confluent failed to increase the content of hemopoietic cells in the culture system. Production of hemopoietic progenitors and differentiated progeny was on the other hand amplified by addition of c-kit ligand at regular intervals from the initiation of the culture, and resulted in net formation of these cells in the culture system. The characteristics of the response were consistent with consequences of increased survival of hemopoietic progenitors during a vulnerable initial phase in which the availability of endogenous c-kit ligand was limited by the initially low number of stromal cells. The increase in differentiated progeny was essentially due to increased formation of neutrophil series, and the lack of increased basophil production under these circumstances presumably reflected the nature of the contributory effects of endogenously generated growth regulatory molecules which acted in a synergistic manner with added c-kit ligand.

Summary. Alterations in neoplastic cell behaviour responsible for increased production of terminally-differentiated granulocytes during long-term culture of bone marrow in different categories of acute leukaemia and myelodysplasia have been investigated. An increase in neutrophils associated with transition to a morphological picture identical to normal control cultures occurred in 15 of 25 studies on acute leukaemia in contrast to one of six studies on myelodysplastic disorders. An abnormal neoplastic karyotype was employed as a marker for monitoring the course of the neoplastic cell population in 11 studies in which there was progression towards a normal pattern of differentiation. An increase in differentiation was shown by this means to represent increased maturation of cells of the neoplastic process in one study on a myelodysplastic disorder, demonstrating domination of proliferative activity in culture by all of the myelodysplastic disorders examined. Transition towards normal differentiation in nine studies on acute leukaemia, however, correlated with partial or complete replacement of the acute leukaemic cells by normal haemopoietic series in de novo acute leukaemia, and by Ph positive cells in blast crisis of CML. Conversion to morphologically and cytogenetically normal cell populations in five studies on de novo acute leukaemia occurred in four cases which failed to respond to remission-induction therapy, suggesting the selective toxic effect capable of purging acute leukaemic cells from bone marrow operated by a mechanism which lacked cross-resistance to currently-employed cytotoxic agents.

Severe iron overload is a reported complication of certain erythroid disorders which are characterized by increased erythropoietic activity. Proposed mechanisms include enhancement of iron absorption secondary to increased erythroid activity and coexistent heterozygosity or homozygosity for haemochromatosis. We performed PCR-based analysis for the haemochromatosis-related HFE C282Y mutation in an extended family with inherited haemolytic anaemia in which several members exhibited iron overload. The results demonstrated iron overload was associated with homozygosity but not heterozygosity for this mutation. Such an association may also exist in other erythroid disorders in which iron overload has been reported.

surrounding the excised cancer exceeded that in the normal thyroid tissue of four other patients with thyroid cancer who had no known exposure to arsenic, and was considered to refl ect retention of arsenic for 10 years after completion of ATO administration that could have promoted the development of thyroid cancer. Th ere are a number of questions as to the extent to which these observations provide evidence of an unequivocal link between tissue retention of arsenic after ATO therapy and an increase in cancer risk. Th e arsenic concentration in thyroid tissue of the unexposed control subjects was highly variable, ranging from virtually negligible to approximately half that in the ATO trioxide treated patient, which in such a limited number of patients prevented statistically signifi cant confi rmation of a diff erence between arsenic concentrations in thyroid tissue of the patient and the subjects who had not

Most cases of iron deficiency can be diagnosed with simple tests. The concentration of serum iron

The characteristics of severe neutropenia with a delayed onset following administration of rituximab have been evaluated in 53 consecutively treated patients. All but one patient received rituximab for the treatment of non-Hodgkin's lymphoma. Eight episodes of grade 4 neutropenia were detected between 1 and 5 months after rituximab, when administered alone on five occasions, and on three occasions in combination with chemotherapy, where neutrophil counts had recovered prior to the development of neutropenia. In three episodes, the patients presented with sepsis. Development of neutropenia did not correlate with either the presence of detectable disease or the administration of further treatment. Neutropenia was associated with selective depletion of neutrophil precursors in all but one episode, where it was associated with generalized bone marrow hypoplasia. All episodes developed after a period of either normal or mildly depressed neutrophil counts following treatment with rituximab, and persisted for between several days and several months, before undergoing spontaneous recovery in four instances, and after administration of filgrastim in the remainder. Episodes of neutropenia were associated with disordered immune status manifested by lymphopenia and hypogammaglobulinaemia, raising the possibility that either disturbance of the balance of lymphocyte subsets or an immune dyscrasia induced by rituximab resulted in the development of this type of neutropenia.

Summary Aims The reported association of glomerular disease with chronic lymphocytic leukaemia (CLL) is rare despite the relative frequency of this type of leukaemia. Hence, we have examined the renal biopsies in three patients with CLL and glomerulonephritis. Methods Renal biopsies were examined by light microscopy, immunofluorescence microscopy and electron microscopy. Results One of two patients with mild impairment of renal function and an active urinary sediment had ultrastructural features of idiopathic type I membranoproliferative glomerulonephritis (MPGN), and the other had features of fibrillary/immunotactoid glomerulonephritis with deposits of IgG and C3. One patient with nephrotic syndrome had characteristic electron microscopic appearances of type III MPGN. In all three there was an association with monoclonal gammopathy. The parameters of glomerular damage improved in association with response to drug treatment of the CLL. Conclusion There is a spectrum of types of MPGN seen in patients with CLL and there appears to be an association with the presence of monoclonal gammopathy. This is the first reported case of type III MPGN in CLL.

BACKGROUND The combination of ATRA and anthracycline-based chemotherapy has traditionally been regarded as the gold standard for induction and consolidation in previously untreated APL patients (pts), with ATO usually reserved for relapse. Recent data in Sanz low-risk (LR) and intermediate-risk (IR) APL indicate ATRA + ATO is superior to ATRA + chemotherapy (N Engl J Med 2013), but the optimal therapy for high-risk (HiR) pts remains unclear. In an attempt to improve anti-leukemic efficacy whilst limiting reliance on anthracyclines for all risk categories of APL, the ALLG incorporated ATO into an ATRA + reduced chemotherapy backbone, and the results of an interim analysis with a median follow-up of 2 years (yr) have been published (Blood 120:1570, 2012). Herein, we report results of the protocol-specified final analysis, conducted when all surviving pts had been followed for at least 2 yr after completion of consolidation. METHODS As published, APML4 protocol treatment comprised: (i) induction with ATRA (45 mg/m2 d1-36), IDA (12 mg/m2 d2,4,6,8), ATO (0.15 mg/kg d9-36), prophylactic prednisone (1 mg/kg d1-10) and aggressive hemostatic support; (ii) consolidation with ATRA and ATO (continuous in cycle 1, intermittent in cycle 2); (iii) 2 yr oral maintenance with ATRA, 6-mercaptopurine and methotrexate. Between 2004-2009, 124 evaluable pts were accrued, and median follow-up by the censor-reversing Kaplan-Meier method in this final analysis is 4.2 yr. RESULTS Median age was 44 (3-78) yr, median white cell count was 2.4 x 109/L (0.1-85.8), and median platelet count 22 x 109/L (2-173). Risk groups were 33 LR, 67 IR, 23 HiR, 1 unknown. FLT3 mutations were present in 44%, and 11% had ≥ 2 additional cytogenetic abnormalities (2+ACA). There were 4 (3.2%) deaths during induction (myocardial infarction d1, cerebral hemorrhage d3 and d7, cerebral edema and seizures d30). Grade 3-4 non-hematological adverse events included differentiation syndrome in 14%, and frequent but reversible biochemical hepatic and gastrointestinal toxicity. Q-Tc prolongation > 500 msec occurred in 14%, but there were no cases of ventricular arrhythmias or torsades de pointe. Significant neurological and cutaneous toxicity were infrequent. After induction, 118 pts (95%) achieved hematological complete remission; 112 commenced consolidation, and all were in molecular remission after cycle 2. A total of 5 relapses and 3 deaths have occurred post-induction, but none of the deaths were attributable to protocol therapy. Severe adverse events were less common during the chemotherapy-free consolidation cycles, especially cycle 2. The frequency of grade 3-4 neutropenia was 62% in cycle 1 and 27% in cycle 2, but there was no grade 3-4 thrombocytopenia. The following table lists event-free survival (EFS), disease-free survival (DFS), overall survival (OS) and cumulative incidence of relapse (CIR): Table All pts LR IR HiR 2 yr 5 yr 2 yr 5 yr 2 yr 5 yr 2 yr 5 yr EFS 92% 90% 97% 97% 93% 89% 83% 83% DFS 97% 95% 100% 100% 97% 93% 95% 95% OS 94% 94% 97% 97% 96% 96% 87% 87% CIR 3% 5% 0% 0% 3% 7% 5% 5% In univariate analysis, 2+ACA predicted for inferior DFS (P = .04), whereas age > 70 was associated with increased risk of early death (ED, P = .02), inferior EFS (P = .0002), and inferior OS (P = .001). Neither Sanz risk category nor FLT3 mutation status was significantly correlated with these outcome endpoints (all P > .05). In multivariate analysis, the significant associations of 2+ACA (P = .04 for DFS) and age > 70 (P = .0002 for EFS, P = .005 for OS) were retained. In addition, Sanz risk category was correlated with EFS (P[trend] = .003) and OS (P[trend] = .02). When compared with our previous ALLG APML3 trial (ATRA + IDA for induction and consolidation without ATO; Haematologica 2012), treatment with APML4 was associated with substantial and statistically significant improvements (see Figure) in EFS (P = .002), DFS (P = .001) and OS (P = .02). The significance of trial assignment was retained in multivariate analysis when APML3 and APML4 data were combined. CONCLUSIONS APML4 is a potent anti-leukemic regimen with manageable toxicity and a low ED rate. EFS and OS remain impressive with mature follow-up, and were influenced primarily by advanced age and Sanz risk category. The CIR was 5%, and was only associated with 2+ACA. Our results support the inclusion of ATO in induction and consolidation as front-line therapy for APL whilst simultaneously limiting cumulative anthracycline exposure. Figure 1 Figure 1. Disclosures Off Label Use: Arsenic trioxide is currently only registered in the US, Europe and Australia for the treatment of relapsed APL. This report includes its use in the initial treatment of APL.

The capacity of multiple myeloma cells to generate parathyroid hormone-related protein (PTHrP) has been examined by in situ assessment of PTHrP mRNA and PTHrP protein in myeloma cells of patients in whom the disease was associated with the development of hypercalcaemia. The presence of PTHrP mRNA was evaluated by in situ hybridization using an antisense riboprobe, and PTHrP by immunohistochemistry using a monoclonal antibody, in archival bone marrow trephine specimens from 17 patients. PTHrP mRNA was detected in myeloma cells in 16 of the 17 patients, indicating a high frequency of PTHrP gene expression in myeloma cells in these subjects. PTHrP protein was, on the other hand, detected in the myeloma cells of only five of these patients. The impact of the mercury-based fixation and decalcification procedure used for processing the bone marrow trephine specimens was assessed to determine the influence of this process on the outcome of the immunohistochemical assay for PTHrP. It was shown that this preparative procedure resulted in a marked reduction of immunohistochemically detectable PTHrP, which provides a possible explanation for the lower frequency of positivity for PTHrP in myeloma cells in the bone marrow specimens. The present findings are consistent with the view that PTHrP can be generated in myeloma cells in vivo, and could contribute to osteolysis and hypercalcaemia, as in patients with cancer.

Summary Disseminated enteric human cytopathogenic orphan (echo) virus infection after allogeneic bone marrow transplantation has been reported once previously: a patient developed a fatal infection with the virus being isolated from brain, lung and heart. We report a second case of disseminated echovirus infection in which virus was isolated from the stomach and liver. On this occasion the infection was associated with the development of biopsy-proven acute graft-versus-host disease of the skin, stomach, colon and liver. The infection resolved without sequelae.

The incidence of hypercalcaemia and its association with humoral mechanisms involving parathyroid hormone-related protein (PTHrP), parathyroid hormone (PTH), or 1,25(OH) 2 vitamin D were assessed in a prospective study of patients admitted to a clinical haematology unit. Hypercalcaemia was detected in 18/165 patients, and was due to primary hyperparathyroidism in 3/17 patients in whom results of humoral mediator assessments were obtained. In the other patients, hypercalcaemia was associated in nine instances with myeloma, in five with B-cell non-Hodgkin's lymphoma (NHL). and in one with myeloid neoplasia. No evidence was obtained of a humoral mechanism involving 1,25(OH) 2 vitamin D, but elevated circulating levels of PTHrP, comparable with those in humoral hypercalcaemia of malignancy, were present in 2/4 patients with NHL, and in 3/9 with myeloma. The relationship between presence or absence of elevated circulating PTHrP, and presence or absence of hypercalcaemia during the course of treatment, indicated PTHrP was involved in the production of hypercalcaemia. Such an association raises the possibility that PTHrP released by neoplastic cells in these disorders acts in a paracrine manner to produce local bone resorption, and when produced in greater amounts causes elevated circulating levels which make an additional humorally-mediated contribution to the development of hypercalcaemia.

Summary Disseminated infection with the fungus Scedosporium inflatum in a neutropenic patient with non-Hodgkins lymphoma presented with the triad of muscle tenderness, papular skin lesions and fever, and progressed rapidly to a fatal outcome. This represents the first reported instance of fatal widely disseminated infection with this organism, and demonstrates that the triad of presenting clinical features, formerly reported to be pathognomic of systemic candidiasis, can no longer be regarded as specific for infection with a particular species of yeast or fungus.

Brief Abstract Protein kinase C beta II expression in diffuse large B-cell lymphoma has prognostic significance not only for CHOP therapy in low-risk International Prognostic Index disease but also for all patients receiving CHOP plus rituximab. Full Abstract Introduction Protein kinase C beta II (PKCbII) expression has been reported to indicate inferior prognosis in diffuse large B-cell lymphoma (DLBCL) treated with anthracycline-based chemotherapy. Aim To compare the prognostic significance of immunohistochemically determined PKCbII expression in de novo DLBCL treated with CHOP chemotherapy (cyclophosphamide/doxorubicin/vincristine/prednisone) with and without rituximab. Patients and Methods 80 consecutive patients treated at St. Vincent's Hospital with de novo DLBCL, 48 treated with CHOP, and 32 with R-CHOP (rituximab plus CHOP), were studied using immunohistochemistry for PKCbII on diagnostic tissue samples. Staining results were correlated with patient characteristics and clinical outcome. Overall survival (OS) and progression-free survival (PFS) were determined by the Kaplan-Meier method, and comparisons were determined by the log-rank test. Results PKCbII expression correlated with inferior OS and PFS in CHOP-treated patients with low-risk International Prognostic Index (IPI) disease (0–2 adverse factors) but not in the overall patient group unstratified by IPI. PKCbII expression significantly correlated with inferior OS and PFS in R-CHOP—treated patients unstratified by IPI status. Conclusion PKCbII expression has prognostic significance not only for CHOP therapy in low-risk IPI disease but also for all patients receiving R-CHOP. Immunohistochemically demonstrated PKCbII expression thus identified patient subgroups in which alternative treatment strategies might confer superior outcome.

:Neutropenia is a life-threatening sequel of hematological disorders and a dominant factor limiting the dosage of cytotoxic chemotherapy. The role of the neutrophil is of such importance in defence against microbial invasion that measures that modify the behaviour of residual hemopoietic tissue to promote a modest increase in neutrophils, can confer considerable benefit by reducing the frequency and severity of infection. Such a change can be mediated in bone marrow depression by diversion of more progeny of immature precursors into the neutrophil series, or by enhancement of the stimulatory drive operating on neutrophil production. The former effect can be achieved by hypertransfusion of red cells to reduce the demand on the limited precursor population for cells of the erythroid series. The latter effect can be achieved by administration of lithium carbonate. Neutropenia caused by autoimmune injury to the neutrophil series can also be successfully modified by measures which suppress the underlying immune dyscrasia or the function of the reticuloendothelial system. Corticosteroid administration and splenectomy can be helpful in certain specific types of neutropenia. Administration of cyclophosphamide and azathioprine has both mutagenic and marrow suppressive potential, but can induce remissions in severe chronic isolated neutropenia and in systemic lupus erythematosis.

Summary: Three cases of pure red cell aplasia (PRCA) are reported. PRCA developed with no apparent cause in the first case, was associated with histiocytic lymphoma in the second and with diphenylhydantoin therapy in the third. In vitro studies showed the presence of toxic factors against erythroid precursors in the second and third cases. It is argued that the absence of such factors in the serum of the first case does not rule out antibody-mediated damage to erythroid precursors in vivo as the demonstration in vitro would require antibody excess in vivo. Steroids induced a remission in the first two cases providing further evidence that an immunological mechanism is responsible for the PRCA. Withdrawal from diphenylhydantoin plus steroid therapy induced a rapid remission in the third case.

Since July 1984, eight patients with advanced hairy cell leukemia have received treatment with recombinant alpha A interferon. At commencement of interferon, seven patients had progressive cytopenia, and one was in leukemic phase (greater than 20 x 10(9)/L circulating hairy cells). All patients had had previous splenectomy. Interferon was administered subcutaneously. The initial dose was 3 x 10(6) U/day, continued until peripheral counts stabilised. Subsequently, patients received 6 x 10(6) U/day, 9 x 10(6) U/day, and finally 12 x 10(6) U/day. The dose increases proceeded every 8-12 weeks, as tolerated. Seven patients had an objective response. There were four complete remissions, two partial remissions, and one minor response. Complete remission was documented only in patients on at least 6 x 10(6) U/day for 12 weeks. The median time to complete remission was 40 weeks (range 35-53). Normalisation of peripheral blood counts preceded histologic marrow improvement. The median times for response (platelets greater than or equal to 100 x 10(9)/L, hemaglobin greater than or equal to 12 gm/dL, neutrophils greater than or equal to 1.5 x 10(9)/L), were six to eight and 17 weeks, respectively. Toxicity included myelosuppression during the first four weeks of therapy. With increasing doses of interferon, myelosuppression did not recur. A transient, mild, flu-like syndrome affected all patients. Two patients developed asymptomatic transaminitis at doses greater than 6 X 10(6) U/day. This resolved with dose reduction. In one case impotence was reported during the first four weeks of each interferon level.(ABSTRACT TRUNCATED AT 250 WORDS)

Summary: Very high serum muramidase concentrations in the absence of renal impairment can serve as a marker of a number of haematological neoplastic disorders, and several cases are described where the presence of these disorders was indicated by this means before the diagnosis could be established on morphological grounds. The suitability of the muramidase assay for this purpose was supported by observations that muramidase concentrations in excess of approximately five times the mean normal value were correlated closely with either chronic granulocytic, acute monocytic or myelomonocytic leukaemia, myelofibrosis or polycythaemia vera. These neoplastic disorders appeared to be effectively distinguished by this criterion from other haematological and inflammatory disorders including reactive monocytic and granulocytic states which produced lesser elevation of the muramidase concentration. On the basis of the present experience, it is suggested that estimation of the serum muramidase concentration is particularly useful in the investigation of suspected leukaemia in refractory sideroblastic anaemia, persistent monocytosis, and pancytopenic states with cellular bone marrow where the morphological picture is difficult to interpret.

A case is described in which polycythaemia vera was found to co-exist with chronic lymphatic leukaemia at the time of presentation. This case can be added to five other reported cases of an association between polycythaemia vera and well-differentiated lymphocytic neoplasia, and adds further emphasis to the tendency for dual presentation, which has now occurred in all but one of these cases. One explanation is that the association is due to chance, but the tendency for dual presentation raises the possibility that the overall picture reflects neoplastic involvement of stem cells with capacity to differentiate into the lymphoid as well as the erythroid, myeloid and megakaryocytic series.

Severe neutropenia due to selective loss from the bone marrow of cells of the entire neutrophil maturation sequence developed in a patient with Goodpasture's Syndrome and was associated with serious infections complicating continuous ambulatory peritoneal dialysis. Involvement of T-lymphocytes in the process affecting the neutrophil series was implicated by the relation between recovery from neutropenia and treatment with antithymocyte globulin (ATG). Azathioprine and corticosteroid administration failed to sustain recovery from neutropenia induced by ATG. It is concluded that ATG can provide a nonmyelotoxic form of therapy for pure white cell aplasia whose effectiveness is independent of responsiveness to other immunosuppressive agents.

In a prospective, controlled trial 26 anaemic, neutropenic children with newly diagnosed acute lymphocytic leukaemia were randomised in pairs to receive either transfusion to a haemoglobin of 10-12 g/dl where clinically indicated (group A) or hypertransfusion to a haemoglobin of 16-18 g/dl (group B). Compared with group A (11 of 13 transfused), group B (all transfused) had a significantly more rapid rise in neutrophils at 7 and 10 days post-transfusion, a lower incidence of infection, and less interruption to chemotherapy. Hypertransfusion restored the myeloid/erythroid ratio to normal in bone-marrow of 5 of 6 children and the proportion of early myeloid precursors was greater than in controls.

Summary: Administration of 5-fluorocytosine in fourteen cases of invasive or systemic fungal infection was accompanied in ten by elimination of the infection. Results which particularly indicated the usefulness of the drug consisted of instances where fungal infections were eliminated following the failure of amphotericin B treatment, and in some patients whose antimicrobial defences had been compromised by immunosuppressive therapy. Success was frequently obtained in infections with Candida and Aspergillus species, as well as in penetrating ocular infections where laboratory identification of the fungus had not been made. The outcome in two cases of Cryptococcus neoformans meningitis was unsatisfactory, and this was shown in one to be due to the emergence of a resistant strain. Toxicity of a minor and reversible nature was encountered in four patients, and consisted of diarrhoea, anaemia or hepatocellular damage.

In this review we have discussed the data which indicates that differentiation can indeed occur to a limited degree in the neoplastic cells in acute leukemia and myelodysplastic syndromes. Attempts to increase the degree of differentiation as an approach to the treatment of these disorders have utilised a variety of chemical agents which have been reported to exert such an effect in vitro. Analysis of the results, however, indicates that beneficial effects of these agents in patients is due to cytotoxic action which selectively reduces the neoplastic cell population. Leukemic cells can also undergo incomplete differentiation in vitro when exposed to appropriate growth factors, which raises the question of whether leukemia and myelodysplasia can be treated by the induction of differentiation in the malignant cells following the administration of these agents. This question, and questions about the nature of complete remission, will be answered in the coming years by clinical trials of growth factors, and further studies of the DNA in mature cells to analyse whether these cells are derived from leukemic progenitors.

Summary Analysis of the bone marrow karyotype in 109 consecutive untreated patients with acute lymphoblastic leukemia (ALL) by the G-banding technique revealed the presence of a translocation between specific sites on the long arms of chromosomes 4 and 11, [t(4;11) (q21;q23)] in 3 adults and 2 children. Splenomegaly was present in all patients, marked leukocytosis in 4, and retinal hemorrhages in the absence of significant mucocutaneous bleeding in 3. Complete remission defined by conventional morphological criteria was achieved with combination chemotherapy in all instances, but the duration of remission was brief in 3. Three patients were studied in relapse, and clonal evolution was found to have occurred in 2. Analysis of our data in conjunction with other published reports suggests this specific karyotypic abnormality characterizes a small subgroup of ALL in which there is a strong association with recognized clinical and laboratory indices of poor prognosis, inparticular its frequent occurrence in children under the age of 2.5 yr. There is a propensity to undergo clonal evolution, and the possibility exists that such a development is associated with poor prognosis

Summary. The action of material released by activated human platelets on the phagocytic activity of human neutrophils and monocytes has been examined under conditions where there was a low background level of exposure of the leucocytes to platelet release products (PRPr). Incubation with PRPr produced an approximate three-fold stimulation of particle ingestion by both cell types. Material with stimulatory activity passed through ultraflltration membranes capable of retaining molecules greater than 500 Daltons. This low molecular weight stimulator was inactivated by ATP diphosphopyrolase to suggest it could be one or more of the nucleotide di- or triphosphates in PRPr. Comparison with the action of specific nucleotides revealed only ADP and ATP exerted equivalent stimulatory effects at concentrations consistent with those of nucleotides normally present in PRPr. This effect was mediated by induction of a change in leucocyte behaviour which was sustained in the absence of continued exposure to the stimulatory agent. Stimulation of phagocytosis was also produced by high molecular weight material in PRPr, but this appeared to be mediated by dissociation of low molecular weight stimulator from a high molecular weight complex. These observations extend the range of biological functions known to respond to nucleotides in PRPr, and have implications for the interpretation of leucocyte phagocytic activity assessed in vitro in view of the potential modification of this process by exposure of leucocytes to PRPr during the isolation of leucocytes from peripheral blood.

The place of cytosine arabinoside (araC) in the treatment of T-cell acute lymphoblastic leukemia was studied by measuring nucleoside transport sites and the conversion of araC to its triphosphate (araCTP) in lymphoblasts from the peripheral blood of two patients, who were then treated with araC. Equilibrium binding of 3H-nitrobenzylmercaptopurine riboside (3H-NBMPR), a specific ligand of the nucleoside transporter, gave 16,510 to 29,400 sites/cell for T-lymphoblasts on presentation or early in relapse compared with 2730 +/- 1570 sites/cell for non-T-lymphoblasts. Accumulation of araCTP from 1 microM araC was four times greater in T-cell than non-T-cell lymphoblasts. One patient was treated with araC (100 mg/m2 daily x 7 days, continuous intravenously) at the time of her first leukemic relapse and complete remission was achieved with this single agent. When this patient relapsed and developed advanced disease the T lymphoblasts showed a 75% reduction in their ability to accumulate araCTP which paralleled a reduction in 3H-NBMPR binding. The second patient achieved complete remission with araC given in low dose (15 mg twice daily by subcutaneous injection) for 21 days at the time of a localised relapse in the mediastinum and pleura. These studies suggest that araC may have a place in the therapy of early stage T-lymphoblastic disease.

The influence of human serum components during in vitro determination of erythropoietin biological activity has been examined in a modified in vitro bioassay procedure utilising rabbit bone marrow as the erythropoietin-responsive tissue. The number of erythroblasts present after 5 d in suspension culture provided a measure of erythropoietin biological activity with a degree of sensitivity equivalent to that provided by estimation of 59Fe incorporation into haem, but possessed the advantage of lacking the susceptibility of the latter method to the level of human serum transferrin saturation. Erythropoietic stimulation was blocked by 10% human serum unless all sera incorporated into the bioassay was previously heated at 56 degrees C. Human serum under the latter conditions was shown to contain material which stimulated erythropoiesis, but which differed in its mode of action from erythropoietin in that it operated by amplifying the response to erythropoietin. Correction for these effects substantially altered interpretation of erythropoietic stimulatory activity of human serum to yield values in keeping with those reported for in vivo bioassay. These findings illustrate the need to clarify the role of human serum components which modify the action of erythropoietin under culture conditions, in view of their potential contribution to discrepancies between values obtained by different bioassay procedures.