Towards the pharmacotherapy of hairy cell leukaemia

Insight into the behavior of hairy cell leukemia by immunogenetic analysis

The B cell receptor (BCR) is the functional distinguishing unit that defines any B cell. Immunoglobulin gene (IG) status is preserved in the neoplastic B cell clone and can provide an indicator of the maturation stage reached by the B cell prior to transformation. In hairy cell leukemia (HCL), several data from IG analysis provide clear hints regarding the cell of origin and the ongoing selective interactions of the tumor BCR with environmental stimuli: HCLs (i) have variable levels of IG somatic mutations, (ii) continue somatic mutations at low levels, (iii) have active processes of IG class switching after transformation, and (iv) have a relatively high frequency of selective events in the light chain of the BCR. It has recently emerged that an unmutated status of the HCL-derived IG can be associated with failure to respond to cladribine, genetic abnormalities indicative of poor outcome, and aggressive disease. These observations suggest that IG gene analysis may have biological and prognostic relevance in HCL and merits further characterization.

Alternative methods of cladribine administration

Nucleoside derivative cladribine treatment in hairy cell leukemia (HCL) is a rare example of treatment success in cancer. In fact, HCL is generally responsive to single-agent cladribine and only a minority of patients are refractory. Cladribine was originally administered intravenously as a continuous infusion at a dose of 0.1 mg/kg/day for 7 consecutive days. Subsequently cladribine has been administered intravenously, as a 2 h infusion for 5 consecutive days or weekly for 7 weeks, or subcutaneously. These regimens are all very effective but often show relevant toxicity. The subcutaneous route is easier to administer and may increase compliance of the patient. We have had the opportunity to investigate the efficacy and toxicity of subcutaneous cladribine given at the dose of 0.1 mg/kg/day for 5 or 7 days as a single course in newly diagnosed HCL requiring treatment, in an ongoing Italian multicenter clinical trial. Overall responses have been no different in the two arms, while a much lower infection rate was observed when cladribine was given at the lowest dose. Subcutaneous administration may be deemed a very convenient route since it does not require hospitalization. A reduced dosage of cladribine may also be advantageous since it may be associated with reduced toxicity and may set the dose needed for combinations with antibody treatments.

Molecular insight into the biology and clinical course of hairy cell leukemia utilizing immunoglobulin gene analysis

The B cell receptor (BCR) is the functional distinguishing unit that defines any B cell. Immunoglobulin gene (IG) status is preserved in the neoplastic B cell clone and can provide an indicator of the maturation stage reached by the B cell prior to transformation. In hairy cell leukemia (HCL), several pieces of data from IG analysis provide clear hints regarding the cell of origin and the ongoing selective interactions of the tumor BCR with environmental stimuli. HCLs have variable levels of IG somatic mutations, and continue somatic mutations at low levels as well as IG class switching after transformation. More recent data also show the occurrence of selective events in the light chain of the BCR, suggesting a dominant role for IG status in the pathogenesis of HCL. Moreover, it has recently emerged that an unmutated status of the HCL IG can be associated with failure to respond to cladribine, genetic abnormalities indicative of poor outcome, and aggressive disease. These observations suggest that IG analysis may have biological and prognostic relevance in HCL and merits further characterization.

Combination therapies to improve the long-term outcome in hairy cell leukemia

Since its first description in 1958, hairy cell leukemia (HCL) had a long period of different unsatisfactory treatments till the early 1980s, when interferon-alfa and subsequently purine analogs (PAs) pentostatin or cladribine, or pentostatin were described to determine durable responses. However, second lines of treatments are very often needed in the life span of patients with HCL and a small minority of patients are refractory and with poor prognosis. These disadvantages have led to test the efficacy of additional compounds, mainly monoclonal antibodies, combined with PAs. The objective of this presentation is to review the current knowledge of combination treatments in HCL. Combination treatments have been used or proposed for different purposes in HCL: to reduce acute toxicity, to improve complete remission (CR) rate, to overcome resistance/refractoriness, to prolong disease-free survival, or to prolong overall survival. The type of patients to be selected for the combinations and the perspectives of combinations of PAs with monoclonal antibodies will also be discussed.

Hairy cell leukemias with unmutated IGHV genes define the minor subset refractory to single-agent cladribine and with more aggressive behavior

Hairy cell leukemia (HCL) is generally responsive to single-agent cladribine, and only a minority of patients are refractory and with poor prognosis. HCLs generally express mutated (M) and, in a minority, unmutated (UM) IGHV. In a multicenter clinical trial in newly diagnosed HCL, we prospectively investigated clinical and molecular parameters predicting response and event-free survival after single-agent cladribine. Of 58 HCLs, 6 expressed UM-IGHV (UM-HCL) and 52 M-IGHV (M-HCL). Beneficial responses were obtained in 53 of 58 patients (91%), whereas treatment failures were observed in 5 of 58 patients (9%). Failures were associated significantly with UM-IGHV (5 of 5 failures vs 1 of 53 beneficial responses had UM-IGHV, P < .001), leukocytosis (3 of 5 vs 3 of 53, P = .006), and bulky spleen (4 of 5 vs 4 of 53, P < .001). The UM-HCL not benefiting from cladribine characteristically had bulky spleen (4 of 5, 80%), leukocytosis (3 of 5, 60%), and TP53 defects (2 of 5, 40%), and progressed rapidly after first treatment (median event-free survival, 7.5 months). Our data suggest that UM-HCLs identify the minor subgroup failing cladribine treatment and with more aggressive disease. High incidence of TP53 dysfunction indicates a potential mechanism of resistance to cladribine in the UM-HCL group. Overall, our data provide new molecular elements relevant for treatment concerns in HCL.

Long-term follow-up of 233 patients with hairy cell leukaemia, treated initially with pentostatin or cladribine, at a median of 16 years from diagnosis

Hairy cell leukaemia (HCL) was first described 50 years ago. Median survival was then 4 years. The purine analogues, introduced in the 1980s, transformed this prognosis. We reviewed data retrospectively from 233 patients, treated with pentostatin (n = 188) or cladribine (n = 45), to investigate the current long-term outlook. Median follow-up was 16 years. There were no significant differences in outcome between the two agents. Overall, the complete response (CR) rate was 80% and median relapse-free survival was 16 years. After relapse (n = 79) or non-response (n = 5), 26 patients received pentostatin and 58 cladribine; 69% achieved CR and median relapse-free survival was 11 years. After third-line therapy (n = 23), 50% achieved CR and median relapse-free survival was 6.5 years. However, CRs were equally durable, whether after first, second or third-line therapy. Complete responders and those with both haemoglobin >100 g/l and platelet count >100 x 10(9)/l before treatment had the longest relapse-free survival (P < 0.0001). Patients still in CR at 5 years had only a 25% risk of relapse by 15 years. Outcomes for patients with recurrent disease improved with the monoclonal antibody rituximab, combined with either purine analogue. Overall only eight patients died of HCL-related causes. Patients achieving a CR can expect a normal lifespan.

Inhibition of HBV gene expression and replication by stably expressed interferon-alpha1 via adeno-associated viral vectors

Background

Interferon‐α2 (IFNα2) is routinely used for anti‐hepatitis B virus (HBV) treatment. However, the therapeutic efficiency is unsatisfactory, particularly in East Asia. Such inefficiency might be a result of the short half‐life, relatively low local concentration and strong side‐effects of interferons. Frequent and repeated injection is also a big burden for patients. In the present study, a single dose of vector‐delivered IFNα1 was tested for its anti‐HBV effects.

Methods

Adeno‐associated viral vector (AAV‐IFNα1) was generated to deliver the IFNα1 gene into hepatocytes. IFNα1, hepatitis B surface (HBsAg) and e (HBeAg) antigens were measured by enzyme‐linked immunosorbent assay and/or western blotting. The level of viral DNA was measured by quantitative real‐time polymerase chain reaction.

Results

AAV‐IFNα1 effectively transduced HBV‐producing cells (HepAD38) and mouse hepatocytes, where IFNα1 was expressed in a stable manner. Both intracellular and extracellular HBsAg and HBeAg were significantly reduced in vitro. In the HBV‐producing mice, the concentration of IFNα1 in the liver was eight‐fold higher than that in plasma. Compared with control groups, HBeAg/HBsAg antigen levels were reduced by more than ten‐fold from day 1–5, and dropped to an undetectable level on day 9 in the AAV‐IFNα1 group. Concurrently, the level of viral DNA decreased over 30‐fold for several weeks.

Conclusions

A single dose administration of AAV‐IFNα1 viral vector displayed prolonged transgene expression and superior antiviral effects both in vitro and in vivo. Therefore, the use of AAV‐IFNα1 might be a potential alternative strategy for anti‐HBV therapy. Copyright © 2008 John Wiley & Sons, Ltd.

High density genome-wide DNA profiling reveals a remarkably stable profile in hairy cell leukaemia

Hairy cell leukaemia (HCL) is a rare B-cell neoplasm for which the molecular mechanisms are largely unknown. High-density genome-wide DNA profiling was performed with Affymetrix 250K arrays to analyse copy number (CN) changes and loss of heterozygosity (LOH) in 16 cases of HCL. Four of 16 cases (25%) demonstrated gross non-recurrent CN deletions. Within the affected regions, we identified genes involved in bone marrow fibrosis (FGF12) and response to treatment (TP53) in individual cases. Large regions (> 5 Mb) of LOH without any concomitant DNA CN changes were identified in 5/16 (31%) HCL and were indicative of uniparental disomy UD. The germline origin of UD was demonstrated in one case for which a matched normal sample was available. Overall analysis of LOH showed that identical loci were recurrently targeted in chromosomes 1, 2 and 6. As a whole, however, HCL showed a remarkably stable genome. This finding adds to several other features that are unique to HCL among mature B-cell tumours.

The role of rituximab in combination with pentostatin or cladribine for the treatment of recurrent/refractory hairy cell leukemia

BACKGROUND

The purine analogs pentostatin and cladribine have revolutionized the treatment of hairy cell leukemia (HCL) with overall responses in greater than 85% of patients and a median progression-free survival of up to 15 years. They continue to be effective at second- and even third-line therapy; however, alternative treatments are needed for patients who are or have become refractory to these agents or whose remissions are shorter with each course of therapy.

METHODS

The authors conducted a retrospective review of 8 patients who received pentostatin or cladribine combined concurrently (n = 6 patients) or sequentially (n = 2 patients) with rituximab at second-line therapy (n = 3 patients) and at subsequent lines of therapy (n = 5 patients). Results from a previously reported database of 219 patients with HCL (73 patients who received second-line therapy and 20 patients who received third-line therapy) were used as a historic control group against which to measure benefit.

RESULTS

All 8 patients responded to therapy, with 7 complete responses (CRs) (87.5%) and minimal toxicity. All patients who had CRs were negative for minimal residual disease (MRD). At a median follow-up of 29 months (range, 5-39 months) 1 patient developed recurrent disease, and the estimated 2-year recurrence rate was 20% (0% after second-line therapy and 25% after subsequent lines of therapy). In the historic control group, the CR rates were 70% after second-line therapy and 45% after third-line therapy, and the recurrence rates at 2 years were 15% and 33%, respectively.

CONCLUSIONS

The combination of purine analogs with rituximab was safe and effective for patients with recurrent and/or refractory HCL, and the current results suggested an added benefit compared with standard treatment.

Therapy of Chronic Lymphocytic Leukaemia with Purine Nucleoside Analogues

Chronic lymphocytic leukaemia (CLL) is a neoplastic disease of unknown aetiology characterised by an absolute lymphocytosis in peripheral blood and bone marrow. The disease is diagnosed most commonly in the elderly with the median age at diagnosis being about 65 years. The purine nucleoside analogues (PNAs) fludarabine, cladribine (2-chlorodeoxyadenosine) and pentostatin (2'-deoxycoformycin) are highly active in CLL, both in previously treated and in refractory or relapsed patients. These three agents share similar chemical structures and mechanisms of action such as induction of apoptosis. However, they also exhibit significant differences, especially in their interactions with enzymes involved in adenosine and deoxyadenosine metabolism. Recent randomised studies suggest that fludarabine and cladribine have similar activity in CLL. However, clinical observations indicate the existence of cross-resistance between fludarabine and cladribine. Patients who received PNAs as their initial therapy and achieved long-lasting response can be successfully retreated with the same agent. PNAs administered in combination with other chemotherapeutic agents and/or monoclonal antibodies may produce higher response rates, including complete response (CR) or molecular CR, compared with PNAs alone or other treatment regimens. Management decisions are more difficult in elderly patients because of the apparent increase in toxicity of PNAs in this population. In elderly patients, we recommend chlorambucil as the first-line treatment, with PNAs in lower doses in refractory or relapsed patients. Myelosuppression and infections, including opportunistic varieties, are the most frequent adverse effects in patients with CLL treated with PNAs. Therefore, some investigators recommend routine antibacterial and antiviral prophylaxis during and after PNA treatment. This review presents current results and treatment strategies with the use of PNAs in CLL, especially in elderly patients.