Homoharringtonine (Omacetaxine Mepesuccinate) in Treating Patients With Chronic Myeloid Leukemia (CML) With the T315I BCR-ABL Gene Mutation

Homoharringtonine (Omacetaxine Mepesuccinate) in Treating Patients With Chronic Myeloid Leukemia (CML) With the T315I BCR-ABL Gene Mutation

A Phase II Open-Label Study of the Subcutaneous Administration of Homoharringtonine. (Omacetaxine) (CGX-635) in the Treatment of Patients With Chronic Myeloid Leukemia. (CML) With the T315I BCR-ABL Gene Mutation

To evaluate the safety and efficacy of subcutaneous administration of omacetaxine mepesuccinate (HHT) in achieving a clinical response in CML patients in chronic, accelerated, or blast phase who have failed prior imatinib therapy and have the T315I kinase domain gene mutation.

Point mutations within the ABL kinase domain of the BCR-ABL gene are emerging as the most frequent mechanism for resistance to imatinib and resultant reactivation of kinase activity. The risk of mutation development is particularly high in patients who are beyond chronic phase, as well as those with a long duration of disease prior to imatinib therapy. The T315I kinase domain (KD) point mutation has merited particular attention, as T315I expressing CML cells are markedly resistant to imatinib. CML patients with the T315I KD mutation, therefore, do not respond to continued treatment with imatinib, and preliminary clinical data indicate that neither of two newer tyrosine kinase inhibitors will have activity in patients with T315I KD mutation either. Omacetaxine mepesuccinate (HHT) is a potent inducer of apoptosis (programmed cell death) in myeloid cells and inhibits angiogenesis (blood vessel formation). In Phase 2 studies, HHT has demonstrated clinical activity in patients with CML, both as a single agent and in-combination with other chemotherapeutic drugs. HHT works via a different mechanism than imatinib or other tyrosine kinase inhibitors (TKI's), and HHT has been shown to inhibit in vitro CML cell lines which harbor the T315I KD mutation and are highly resistant to imatinib. Therefore, CML patients who have the T315I KD mutation may still respond to treatment with HHT. HHT may therefore be an attractive therapeutic option for patients with the T315I KD mutation. On this basis, a multicenter clinical trial is being conducted of HHT therapy for CML patients who have failed prior imatinib therapy and have the T315I KD mutation. Patients will be treated with an induction course consisting of subcutaneous (SC) HHT twice daily for 14 consecutive days every 28 days. Patients who demonstrate a response, may receive maintenance therapy for up to 24 months, consisting of subcutaneous (SC) HHT twice daily for 7 days every 28 days.

Chronic Myeloid Leukemia, CML, HHT, Homoharringtonine, Omacetaxine, T315i, ChemGenex, ChemGenex Pharmaceuticals

Treatment was the same for all cohorts: induction therapy was subcutaneous (SC) administration of omacetaxine at 1.25 mg/m^2 twice a day (BID), administered for 14 consecutive days every 28 (±3) days for up to 6 cycles. Maintenance therapy was subcutaneous (SC) administration of omacetaxine at 1.25 mg/m^2 twice a day (BID), administered for 7 consecutive days every 28 (±3) days for up to 3 years.

Induction: 1.25 mg/m^2 subcutaneously, twice daily for 14 consecutive days every 28 days until response. Patients not demonstrating evidence of clinical response after 6 induction cycles will be considered for removal from the study. Maintenance: 1.25 mg/m^2 subcutaneously, twice daily for 7 consecutive days in a 28-day cycle, for up to 3 years.

Percentage of Participants Achieving an Overall Hematologic Response by Subpopulation and Total Population

Subpopulations reflect chronic myeloid leukemia (CML) phases at the time of enrollment: chronic, accelerated, and blast phase. Primary endpoints as adjudicated by the Data Monitoring Committee were used for the primary analyses. Overall hematologic response for chronic phase participants includes confirmed complete hematologic response (CHR). Overall hematologic response for accelerated or blast phase participants includes confirmed complete hematologic response (CHR), no evidence of leukemia (NEL), or return to chronic phase (RCP). Hematologic response must last >= 8 weeks to be considered meaningful. Response rates by disease phase were examined relative to an a priori value of 2.5% using a one-sided lower 95% exact binomial confidence limit. If the lower limit from the one-sided lower 95% confidence limit exceeds 2.5%, the observed response rate will have exceeded the minimum threshold required to demonstrate efficacy.

Percentage of Participants Achieving a Major Cytogenetic Response by Subpopulation and Total Population

Subpopulations reflect chronic myeloid leukemia (CML) phases at the time of enrollment: chronic, accelerated, and blast phase. Primary endpoints as adjudicated by the Data Monitoring Committee were used for the primary analyses. Major cytogenetic response includes complete or partial response. Both confirmed and unconfirmed major cytogenetic response is considered meaningful. Unconfirmed response is based on a single bone marrow cytogenetic evaluation for participants where a confirmatory evaluation is not available. Complete response shows 0% Philadelphia chromosome positive (Ph+) cells. A partial response shows >0% - 35% Ph+ cells. Response rates by disease phase were examined relative to an a priori value of 2.5% using a one-sided lower 95% exact binomial confidence limit. If the lower limit from the one-sided lower 95% confidence limit exceeds 2.5%, the observed response rate will have exceeded the minimum threshold required to demonstrate efficacy.

TEAE are any untoward events that were newly occurring or worsening from Baseline. Treatment related toxicity was considered by the investigator to be unrelated, possibly, probably or unknown related to study drug. Severity was graded according to the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) v3.0 on the following scale: Grade 1 = mild, Grade 2 = moderate, Grade 3 = severe, Grade 4 = life-threatening, Grade 5 = death. A serious adverse event (SAE) is any untoward medical occurrence that is fatal or life-threatening; results in persistent or significant disability or incapacity; requires or prolongs in-patient hospitalization; is a congenital anomaly/birth defect in the offspring of a patient; and conditions not included in the above that may jeopardize the patient or may require intervention to prevent one of the outcomes listed above. A participant is only counted once in each category (at worst severity or strongest relationship).

Percentage of Participants in Each Cytogenetic Response Category Representing the Degree of Suppression of the Philadelphia Chromosome (Ph+)

Cytogenetic response categories: Complete: 0% Ph+ cells Partial: >0%-35% Ph+ cells Minor: >35%-65% Ph+ cells Minimal: >65%-95% Ph+ cells No Response: >95% Ph+ cells Unevaluable: <20 metaphases were examined and/or response could not be assigned

Percentage of Participants With Major Molecular Response (MMR) Representing the Degree of Suppression of BCR-ABL Transcript Levels Using the Housekeeping Gene GUS

MMR is defined as a ratio of BCR-ABL/standard gene of less than 0.1% according to the international scale. BCR-ABL is a fusion gene of the breakpoint cluster region [BCR] gene and Abelson proto-oncogene [ABL] genes). This analysis used the standard gene GUS. Analysis was performed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) of peripheral blood.

Percentage of Participants With Major Molecular Response (MMR) Representing the Degree of Suppression of BCR-ABL Transcript Levels Using the Housekeeping Gene ABL

MMR is defined as a ratio of BCR-ABL/standard gene of less than 0.1% according to the international scale. BCR-ABL is a fusion gene of the breakpoint cluster region [BCR] gene and Abelson proto-oncogene [ABL] genes). This analysis used the standard gene ABL. Analysis was performed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) of peripheral blood.

Complete Response (CHR) Chronic phase must last at least 8 weeks: WBC <10*10^9/liter, platelets <450*10^9/liter, myelocytes + metamyelocytes <5% in blood, no blasts or promyelocytes in blood, <20% basophils in peripheral blood, no extramedullary involvement. Accelerated and Blast phase must last at least 4 weeks: absolute neutrophil count 1.5*10^9/liter, platelets 100*10^9/liter, no blood blasts, bone marrow blasts <5%, no extramedullary disease. Partial Response - CHR plus one or more of the following: Persistence of splenomegaly with a reduction of ≥50% from pre-treatment Platelets > 450*10^9/L Presence of immature cells in the peripheral blood 5% to 25% blasts in the bone marrow If extra-medullary disease pre-treatment, reduction by ≥50% Hematologic Improvement - CHR, except allowing persistent thrombocytopenia (<100*10^9/L), and a few immature cells No evidence of leukemia: Morphologic leukemia-free state, defined as <5% bone marrow blasts.

Percentage of Participants With Extramedullary Disease (EMD) at Baseline Achieving a Clinical Response

Clinical response was defined by disease phase and based on evaluations by the independent Data Monitoring Committee (DMC). Chronic Phase subgroup: achieving a complete hematologic response and/or major cytogenetic response (complete cytogenetic response or partial cytogenetic response, confirmed or unconfirmed). Accelerated Phase and Blast Phase subgroups: achieving complete hematologic response, no evidence of leukemia, return to chronic phase, and/or major cytogenetic response (complete cytogenetic response or partial cytogenetic response, confirmed or unconfirmed). The percentage of participants achieving response with extramedullary disease at Baseline was to be summarized, if the sample size was sufficient. This analysis was not done as the sample was ultimately insufficient

Percentage of Participants With the Largest Percentage Reduction From Baseline of T315I Mutated BCR-ABL

Summarization is based on the best of the individual response assessments. Not assessable indicates that the participant either had no baseline assessment or the % mutation could not be determined in the post-baseline assessment(s).

Induction therapy was administered for 14 consecutive days for each 28 days cycle, for up to 6 cycles. All treatment arms were given omacetaxine mepesuccinate via subcutaneous (SC) administration at 1.25 mg/m^2 twice a day (BID) for the 14 consecutive days.

Time to onset was analyzed using Kaplan-Meier estimates. Participants who did not achieve a response are censored at their last visit day. Overall hematologic response for chronic phase participants includes confirmed complete hematologic response (CHR). Overall hematologic response for accelerated or blast phase participants includes confirmed complete hematologic response (CHR), no evidence of leukemia (NEL), or return to chronic phase (RCP). Hematologic response must last >= 8 weeks to be considered meaningful.

Time to onset was analyzed using Kaplan-Meier estimates. Participants who did not achieve a response are censored at their last visit day. Major cytogenetic response includes complete or partial response. Both confirmed and unconfirmed major cytogenetic response is considered meaningful. Unconfirmed response is based on a single bone marrow cytogenetic evaluation for participants where a confirmatory evaluation is not available. Complete response shows 0% Philadelphia chromosome positive (Ph+) cells. A partial response shows >0% - 35% Ph+ cells.

Duration of response is defined as the time from first reported date of hematologic response until the earliest date of objective evidence of disease progression, relapse or death. Data was censored at the last examination date for participants with ongoing response or participants who discontinued treatment for reasons other than adverse event, disease progression or death.

Duration of response is defined as the time from first reported date of cytogenetic response until the earliest date of objective evidence of disease progression, relapse or death. Data was censored at the last examination date for participants with ongoing response or participants who discontinued treatment for reasons other than adverse event, disease progression or death.

Time to disease progression is defined as the time from the initiation of treatment until the onset date of death, the development of CML accelerated phase or blast phase, or the loss of complete hematologic response or major cytogenetic response, whichever came first. Participants were censored only if they did not have progression or if they discontinued treatment for reasons other than AE, progression or death.

Overall survival is defined as the time from the initiation of treatment until death from any cause or the last day of participant contact or evaluation for participants that were lost to follow-up. Participants were censored t the last recorded contract or evaluation when a participant was alive at time of analysis. A quarterly phone survey was conducted to collect survival data for participants who discontinued from the study.

Inclusion Criteria: Male or female patients, age 18 years or older Philadelphia chromosome (Ph) positive chronic myelogenous leukemia in either chronic, accelerated, or blast phase The patient will have the T315I BCR-ABL gene mutation Patients will have failed prior imatinib therapy ECOG performance status 0-2 Exclusion Criteria: NYHA class III or IV heart disease, active ischemia or any other uncontrolled cardiac condition such as angina pectoris, clinically significant cardiac arrhythmia and requiring therapy, uncontrolled hypertension or congestive heart failure Myocardial infarction in the previous 12 weeks Lymphoid Ph+ blast crisis

Cortes J, Lipton JH, Rea D, Digumarti R, Chuah C, Nanda N, Benichou AC, Craig AR, Michallet M, Nicolini FE, Kantarjian H; Omacetaxine 202 Study Group. Phase 2 study of subcutaneous omacetaxine mepesuccinate after TKI failure in patients with chronic-phase CML with T315I mutation. Blood. 2012 Sep 27;120(13):2573-80. doi: 10.1182/blood-2012-03-415307. Epub 2012 Aug 15.