SAA patients benefit from upfront eltrombopag combo

Compared to historic rates for patients on hATG and CsA alone, “the addition of eltrombopag resulted in over 20% higher overall response rates and complete response rates for both 3 and 6 months,” Dr Townsley said.

“And for cohort 3, when eltrombopag is given on day 1, the rate of response in evaluable patients to date appears even higher, with 95% overall response rate at 6 months, of which 60% are complete.”

Dr Townsley also noted that, compared to historical experience, neutrophil recovery was more robust in responding patients treated with eltrombopag. Patients on eltrombopag had a mean ANC of 2253/μL, compared with an ANC of 1716/μL for the historic comparator.

“And likewise, more robust platelet recovery was observed with eltrombopag,” Dr Townsley said, with the eltrombopag-treated patients achieving a mean count of 115,262/μL, compared to a mean of 84,303/μL for the historic group.

She added that, among all eltrombopag-treated patients, the median time to neutrophil recovery was 29 days for an ANC greater than 200/μL and 47 days for an ANC greater than 500/μL. In cohort 3—in which eltrombopag was initiated on day 1—those endpoints were achieved in a median of 8 days and 38 days, respectively.

Patients became transfusion-independent for red cells in a median of 42 days and for platelets in a median of 32 days.

Eltrombopag-treated patients had a 99% overall survival at a median follow-up of 18 months (range 1 – 42) when censored for stem cell transplant. When not censored for transplant, their overall survival was 97%.

Adverse events

“The addition of eltrombopag to ATG and cyclosporine was, overall, well tolerated,” Dr Townsley said. “Few grade 3 to 4 events were attributed to eltrombopag.”

Severe cutaneous reactions in 2 patients caused eltrombopag to be stopped, and 10% of patients had grade 2–3 transaminase and bilirubin elevations.

Bone marrow biopsies revealed no increased fibrosis.

One patient with thymoma died while on study due to encephalopathy. And 2 deaths occurred after hematopoietic stem cell transplant, one with relapsed acute myeloid leukemia and the other from relapsed aplastic anemia.

Clonal evolution occurred in 7 patients, 2 who had achieved CR and evolved in 3 and 30 months. Neither patient had bone marrow dysplasia. One patient’s cytogenetics normalized, and the other had stable disease.

“In our protocol, we define any new cytogenetic abnormality as clonal evolution—we have always done this,” Dr Townsley said.

Of the other 5 patients who evolved, 1 achieved a CR and relapsed, 1 achieved a PR and relapsed, 2 achieved a PR, and 1 had no response. Three of these patients had stem cell transplants, 1 had stable disease, and 1 died of acute myeloid leukemia after stem cell transplant.

The investigators concluded that eltrombopag increases complete and overall hematologic response rates in treatment-naïve SAA patients. Immediate introduction of eltrombopag with immunosuppressant therapy may be optimal, and CR does not appear to prevent clonal evolution.

Investigators are currently in the process of conducting a long-term, serial genomic analysis. The study is open for accrual to an extension cohort.

Eltrombopag is marketed as Promacta in the US and Revolade in most countries outside the US.

Dr Townsley disclosed drug and research funding from GlaxoSmithKline and Novartis, developers of eltrombopag.

*Data in the abstract differ from the presentation.