Long-term Follow Up Interim Data Show Nplate(TM) Increased And Sustained Platelet Counts In Adult Chronic ITP Patients

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Long-term Follow Up Interim Data Show Nplate Increased And Sustained

Platelet Counts In Adult Chronic ITP Patients

09 Dec 2008

Amgen Inc. (Nasdaq: AMGN) released updated results from the ongoing, open-label

extension study of the long-term safety and efficacy of Nplate (romiplostim)

in adult patients with chronic immune thrombocytopenic purpura (ITP). Chronic

ITP is a chronic and serious autoimmune disorder characterized by lower than

expected platelet counts in the blood, sometimes leading to serious bleeding

events. The results were presented as an oral presentation at the 50th Annual

Meeting of the American Society of Hematology (ASH Abstract # 402). Results from

a study of Nplate in myelodysplastic syndromes (MDS) also were presented.

" These data show Nplate increased platelet counts in most patients for most of

the time, and clinically relevant bleeding was reduced over time, " said J.

Kuter, M.D., Chief of Hematology, Massachusetts General Hospital, Boston. " This

is significant because Nplate can be a long-term treatment for adult chronic ITP

patients, who are at risk of serious bleeding events if their platelet counts

drop to less than 30,000 per microliter. These patients have had limited

availability to long term treatment options. "

These study results showed that overall 74 percent of patients (160/215)

achieved a platelet response defined as a platelet count of 50,000 platelets per

microliter and doubling of the baseline platelet count (median:17,000 platelets

per microliter). A platelet response was achieved by 30 percent (61/207) of

patients after the first dose and by 47 percent (94/199) of patients after the

third dose. The average treatment period was 76 weeks and the longest duration

of treatment was 204 weeks.

Additional key findings from the Extension study show:

-- Platelet counts increased: Platelet counts of Nplate-treated patients were

increased from baseline by 20,000 platelets per microliter more than 80 percent

of the time in 47 percent of patients and more than half the time in 67 percent

of patients.

-- Platelet counts maintained: Platelet count increases of 50,000 platelets per

microliter were sustained for greater than or equal to 10, greater than or equal

to 25, and greater than or equal to 52 consecutive weeks in 77 percent

(127/164), 67 percent (95/141), and 41 percent (48/116) of patients,

respectively.

In this study, adverse events (AEs) did not increase with time and were reported

in 86 percent of patients, with most mild to moderate in severity. The most

common were headache (34 percent), contusion (32 percent), and fatigue (31

percent). Treatment-related and serious AEs were reported in 28 percent and 29

percent of patients, respectively. Treatment-related serious AEs were reported

in 7 percent of patients. Five percent of patients (11/215) discontinued

treatment due to AEs.

Bone marrow reticulin was present or increased in eight patients with no

evidence of progression to collagen fibrosis or chronic idiopathic

myelofibrosis. Thrombotic/thromboembolic events were reported in seven patients,

of whom six had pre-existing risk factors. To date, one patient developed a

neutralizing antibody to Nplate; however, it did not cross react with

thrombopoietin and it was absent upon re-testing four months after Nplate

treatment was stopped.

This ongoing, open-label study is assessing the safety and efficacy of long-term

administration of Nplate in both splenectomized and non-splenectomized adult

chronic ITP patients. As of July 2008, 223 patients had enrolled and 215 were

treated with Nplate. Sixty-one percent of patients were female and, of the

enrolled patients, 44 percent had undergone a splenectomy (removal of the

spleen).

Eligible patients had completed a previous ITP Nplate study, with no significant

change in medical history. The Nplate starting dose was 1 ug/kg by subcutaneous

injection and was adjusted to maintain a platelet count between 50,000 and

200,000 platelets per microliter.

Interim Phase 2 Nplate MDS Data Also Presented (Abstract # 224)

Interim data from an ongoing Phase 2 multicenter, randomized, double-blind,

placebo-controlled study evaluating Nplate in patients with low or intermediate

risk MDS receiving azacytidine were also presented (n=40). The interim analysis

showed that Nplate reduced the incidence of clinically significant,

treatment-related thrombocytopenic events and platelet transfusions. Nplate also

improved the platelet nadir, defined as the lowest peripheral blood count that

occurs secondary to bone marrow suppression, in MDS patients receiving

azacytidine.

Each study arm was in combination with azacytidine, and serious AEs were

observed in 77 percent of the placebo group, 46 percent of the Nplate 500ug

group and 71 percent of the 750ug group. One incident of each of the following

events was reported: arthralgia, rash, hypersensitivity, pulmonary hemorrhage,

hemorrhage and epistaxis. Two patients in the placebo group died, one of fungal

pneumonia and the other of pulmonary hemorrhage. One case of disease progression

from MDS to acute myeloid leukemia was observed in the Nplate 500ug treated

group.

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