On June 12, 2015 Agios Pharmaceuticals reported new data from the dose-escalation phase and expansion cohorts from the ongoing Phase 1 study evaluating single agent AG-221, a first-in-class, oral, selective, potent inhibitor of mutant isocitrate dehydrogenase-2 (IDH2), in advanced hematologic malignancies (Press release, Agios Pharmaceuticals, JUN 12, 2015, View Source;p=RssLanding&cat=news&id=2058805 [SID:1234505404]). The data will be presented at the 20th Congress of the European Hematology Association (EHA) (Free EHA Whitepaper) taking place June 11-14, 2015 in Vienna.

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Data as of May 1, 2015 from 177 patients (104 in dose escalation and 73 from the first four expansion cohorts) with advanced hematologic malignancies treated with single agent AG-221 showed durable clinical activity and a favorable safety profile. More than half of the 177 patients remain on treatment. The study had an overall response rate of 40 percent (63 of 158 response-evaluable patients, using the criteria below) and a complete remission rate of 16 percent (26 of 158 response-evaluable patients). Patients responding to AG-221 continue to show durable clinical activity on treatment for more than 15 months, with an estimated 76 percent of responders staying on treatment for six months or longer. The overall safety profile observed was consistent with previously reported data with more than 100 additional patients treated as of the last analysis.

This new data reflects responses in the evaluable population, which includes all patients with a pre-AG-221 screening assessment and day 28 or later response assessment or an earlier discontinuation for any reason. Patients with a screening assessment who were still on treatment, but had not reached the day 28 disease assessment, were excluded.

"The clinical profile of AG-221 continues to be impressive from the perspectives of response rate, durability, safety and unique mechanism of action," said Courtney DiNardo, M.D., lead investigator and assistant professor, leukemia at University of Texas MD Anderson Cancer Center. "Additionally, it is encouraging to see early proof-of-concept in myelodysplastic syndrome (MDS) and untreated acute myeloid leukemia (AML) given the need for more effective therapies for these patients."

"As the data from the AG-221 study continue to mature, we are compiling a robust dataset to quickly move this program into global registration studies later this year in collaboration with Celgene," said Chris Bowden, M.D., chief medical officer of Agios. "We are excited about the speed of enrollment we’ve seen to date in our four expansion cohorts and are on track to enroll our recently announced fifth expansion cohort of 125 patients with relapsed and/or refractory AML. With this progress, we are executing on our strategy to combine speed and breadth to reach people with hematologic malignancies in urgent need of better treatments."

About the Ongoing Phase 1 Trial for AG-221 in Advanced Hematologic Malignancies

AG-221 is currently being evaluated in an ongoing Phase 1 trial that includes a dose-escalation phase and four expansion cohorts of 25 patients each, evaluating patients with relapsed or refractory AML who are 60 years of age and older and transplant ineligible; relapsed or refractory AML patients under age 60; untreated AML patients who decline standard of care chemotherapy; and patients with other IDH2-mutant positive hematologic malignancies. Data reported here are from patients receiving AG-221 administered from 60 mg to 450 mg total daily doses in the dose escalation arm and 100 mg once daily in the first four expansion arms, as of May 1, 2015. The median age of these patients is 69 (ranging from 22-90). Treatment with AG-221 showed substantial reduction in the plasma levels of the oncometabolite 2-hydroxglutarate (2HG) to the level observed in healthy volunteers.

Safety Data

A safety analysis was conducted for all 177 treated patients as of May 1, 2015.

The majority of adverse events reported by investigators were mild to moderate, with the most common being nausea, fatigue, increased blood bilirubin and diarrhea.

The majority of serious adverse events (SAE) were disease related; SAEs possibly related to study drug were reported in 27 patients.
A maximum tolerated dose (MTD) has not been reached.
The all-cause 30-day mortality rate was 4.5 percent.

Efficacy Data

Sixty-three out of 158 response-evaluable patients achieved investigator-assessed objective responses for an overall response rate of 40 percent as of May 1, 2015.

Of the 63 patients who achieved an objective response, there were 26 (16 percent) complete remissions (CR), three CRs with incomplete platelet recovery (CRp), 14 marrow CRs (mCR), two CRs with incomplete hematologic recovery (CRi) and 18 partial remissions (PR).
Of the 111 patients with relapsed or refractory AML, 46 (41 percent) achieved an objective response, including 20 (18 percent) CRs, one CRp, 16 PRs, eight mCRs and one CRi.

Of the 22 patients with AML that had not been treated, seven achieved an objective response, including three CRs, two PRs, one mCR and one CRi.

Of the 14 patients with myelodysplastic syndrome (MDS), seven achieved an objective response, including two CRs, one CRp and four mCRs.

Responses were durable, with duration on study drug more than 15 months and ongoing. As of the analysis date, an estimated 88 percent of responses lasted three months or longer, and 76 percent of responses lasted six months or longer.

Upcoming Milestones for AG-221

Agios studies in IDH2-mutated solid and hematologic tumors are ongoing or planned for 2015 to further support development of AG-221.

Continue to enroll patients in the fifth expansion cohort of 125 patients with IDH2 mutant-positive AML who are in second or later relapse, refractory to second-line induction or re-induction treatment, or have relapsed after allogeneic transplantation.

Initiate combination trials to evaluate AG-221 as a potential frontline treatment for patients with AML and a broad range of hematologic malignancies in the second half of 2015.

Initiate a global Phase 3 registration-enabling study in relapsed/refractory AML patients that harbor an IDH2 mutation in the second half of 2015.

Continue dose escalation in the Phase 1/2 trial in patients with advanced solid tumors, including glioma and angioimmunoblastic T-cell lymphoma (AITL) that carry an IDH2 mutation in 2015.