Abstract
Introduction
Ofatumumab is a novel anti-CD20 monoclonal antibody which led to impressive single-agent responses of 47-58% in a phase 2 study of CLL patients (pts) with refractory disease (Wierda et al 2010). Unfortunately, response durations were short (median 5.6-7.1 mos). In order to improve upon these results, we combined ofatumumab with a novel pan-AKT kinase inhibitor, afuresertib (GSK2110183). The AKT pathway plays a centralized role in tumor differentiation, migration, proliferation and survival and is frequently aberrantly activated in CLL (Longo et al 2007). Single agent afuresertib is very well-tolerated with minimal myelotoxicity in relapsed/refractory hematologic malignancies (Spencer et al ASH 2011). We present an interim analysis of the initial 19 of 31 planned pts in an ongoing trial of ofatumumab and afuresertib in relapsed/refractory CLL.
Methods
Previously treated CLL pts who have received at least one prior fludarabine-containing regimen with disease progression are eligible. During the initial 6 month Treatment Phase, ofatumumab 2000mg IV is administered weekly for 8 doses, then once every 4 week cycle for 4 doses (dose/schedule identical to the pivotal phase 2 trial) with afuresertib 125mg orally daily. An initial 10 day Lead-in Phase with afuresertib alone allows for evaluation of pharmacodynamic (PD) changes in phosphoproteins and pharmacokinetic (PK) studies. Pts are assessed for safety and response on day 1 of each cycle. Pts achieving SD, PR or CR by the end of the Treatment Phase proceed to the Maintenance Phase with single-agent afuresertib for a maximum of 12 mos (12 cycles).
Results
Demographics: To date, 19 pts have been enrolled. Median age is 65 yrs (range 43-76), baseline median Hb 108g/L (range 80-145), absolute lymphocytes 29.7 x109/L (range 1.0-464.9), β2M 4.42mg/L (range 1.42-3.21), bulky nodes ≥5cm in 5 pts (32%), organomegaly in 8 pts (42%), del17p/del11q on FISH in 9 pts (47%), and ZAP70+ in 13 pts (68%). Eight pts (42%) were fludarabine-refractory; only 2 pts had received prior alemtuzumab. The median number of prior therapies was 2 (range 1-6).
Toxicity: Hematologic: 4 pts (21%) developed Gr 3-4 neutropenia during at least 1 cycle; 1 pt (5%) had a febrile neutropenia event. Only 2 pts (10.5%) have developed Gr 3-4 thrombocytopenia, without bleeding. Nonhematologic toxicity: Most common related grade 3-4 toxicities were GI: dyspepsia (53%), diarrhea (37%), nausea (21%), temporally related to oral afuresertib and easily managed symptomatically. Infusion reactions to ofatumumab were frequent (12 pts; 63%) with grade 3 reactions in 3 pts. Five pts (26%) developed non-infectious pneumonitis, with 3 pts requiring hospitalization. Two pts with preexisting atrial arrhythmias sustained exacerbation with weekly ofatumumab infusions. Most infections were mild, with only 1 grade 3 cellulitis.
Efficacy: Of the 19 response-evaluable pts receiving a median of 6 cycles (range 1-9), 8 pts (42%) have achieved a PR, 11 SD (58%), and no CR. Response onset was rapid at a median 0.9 mos (range 0.8-2.8). At a median follow-up of 6.8 mos (range 0.3-12.9 mos), 5 pts (26%) have progressed and one patient has died after cycle 1 on therapy due to progressive CLL.
PD Studies: CD19+ cells are assayed for phosphorylated AKT and its downstream targets RAS40 and GSK3 in addition to phospho-proteins of alternative pathways including ERK and pS6 by multiplexed phospho-flow cytometry. Peripheral blood samples are collected at screening and on cycle 1 day 10, after dosing with afuresertib. Of the 7 patients evaluated thus far, 5 demonstrated constitutive AKT phosphorylation at baseline. Partial inhibition of AKT signaling evidenced by increased phosphorylation of AKT and inhibition of GSK3 and/or RAS40 phosphorylation in response to BCR stimulation was observed post-treatment, indicating target engagement by afuresertib. PK Studies: Afuresertib exposure (Cmax and AUC) was similar when afuresertib was administered alone or in combination with ofatumumab.
Conclusion
Preliminary results from this phase 2 study suggests that a combination of ofatumumab plus a novel oral AKT inhibitor, afuresertib, has activity in previously treated CLL and is generally well-tolerated with minimal myelotoxicity. Response data are encouraging but whether durable responses can be achieved requires more mature follow-up.
Disclosures:
Chen: Johnson & Johnson: Consultancy, Research Funding; Lundbeck: Consultancy; Celgene: Consultancy, Research Funding; GlaxoSmithKline: Research Funding; Roche: Honoraria. Off Label Use: Off-label use of ofatumumab and afuresertib for the treatment of relapsed/refractory CLL. Smith:GSK: Employment, Equity Ownership. Johnston:Roche: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Lundbeck: Membership on an entity’s Board of Directors or advisory committees, Research Funding; GSK: Membership on an entity’s Board of Directors or advisory committees, Research Funding.
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