– TIBSOVO® Is the First and Only IDH1 Inhibitor to Be Evaluated in a Phase 3 Clinical Trial for IDH1-Mutant Cholangiocarcinoma –

SUZHOU, China, May 19, 2020 -- The partner of CStone Pharmaceuticals (“CStone”, HKEX: 2616), Agios Pharmaceuticals, Inc. announced that The Lancet Oncology has published data from its global Phase 3 ClarIDHy study of TIBSOVO® (ivosidenib) in previously treated cholangiocarcinoma patients with an isocitrate dehydrogenase 1 (IDH1) mutation. The study met its primary endpoint, demonstrating a statistically significant improvement in progression-free survival (PFS) in patients randomized to TIBSOVO® compared with placebo patients. The safety profile observed in the study was consistent with previously published data. Data from this study were previously presented at the European Society for Medical Oncology Congress (ESMO), held in September 2019 in Barcelona, Spain.

The publication can be accessed at the following link:

https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(20)30157-1/fulltext

ClarIDHy Phase 3 Trial

The ClarIDHy trial is a global, randomized Phase 3 trial in previously treated IDH1-mutant cholangiocarcinoma patients who have documented disease progression following one or two systemic therapies in the advanced setting. Patients were randomized 2:1 to receive either single-agent TIBSOVO® 500 mg once daily or placebo with crossover to TIBSOVO® permitted at the time of documented radiographic progression per RECIST 1.1. At the time of the primary analysis, a total of 185 patients were randomized, with 124 patients in the TIBSOVO® arm and 61 patients in the placebo arm. Thirty-five patients randomized to placebo (57.4%) crossed over to open-label TIBSOVO® upon radiographic disease progression and unblinding.

Results of the study were as follows:

• Median PFS for patients randomized to TIBSOVO® was 2.7 months compared to 1.4 months with placebo (hazard ratio [HR]=0.37; 95% CI [0.25, 0.54], one-sided p<0·0001) as assessed by independent radiology review.
• The estimated PFS rate was 32% at six months and 22% at 12 months for patients randomized to TIBSOVO®, while no patients randomized to placebo were free from progression beyond six months as of the data cut-off.
• The most common treatment-emergent adverse events (AEs) of any grade for the 121 patients who received TIBSOVO® were nausea (36%), diarrhea (31%) and fatigue (26%).
• Less than third of patients experienced serious AEs in either arm (30% of 121 who received TIBSOVO®  versus 22% of 59 patients who received placebo).
• The most common Grade 3 or worse AE in both treatment groups was ascites (nine [7%] of 121 patients who received TIBSOVO®  and four [7%] of 59 patients who received placebo).
• Patients randomized to placebo experienced a significantly greater decline in physical functioning from baseline compared to patients randomized to ivosidenib on the first day of their second 28-day treatment cycle based on European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) Physical Functioning subscale scores (p=0.0059).

TIBSOVO® is not approved in any country for the treatment of patients with previously treated advanced IDH1-mutant cholangiocarcinoma.

About Cholangiocarcinoma

Cholangiocarcinoma (CC) is a rare cancer of the bile ducts within and outside of the liver. Cases that occur within the liver are known as intrahepatic cholangiocarcinoma (IHCC) and those that occur outside the liver are considered extrahepatic. Mutations in IDH1 occur in up to 20% of IHCC cases. Current treatment options for localized disease include surgery, radiation and/or other ablative treatments. There are no approved systemic therapies for IDH1-mutated cholangiocarcinoma and limited chemotherapy options are available in the advanced setting. Gemcitabine-based chemotherapy is often recommended for newly diagnosed advanced or metastatic disease.

About TIBSOVO® (ivosidenib)

TIBSOVO® is indicated for the treatment of acute myeloid leukemia (AML) with a susceptible isocitrate dehydrogenase-1 (IDH1) mutation as detected by an FDA-approved test in:

Adult patients with newly-diagnosed AML who are ≥75 years old or who have comorbidities that preclude use of intensive induction chemotherapy.

Adult patients with relapsed or refractory AML.

About CStone

CStone Pharmaceuticals (HKEX:2616) is a biopharmaceutical company focused on developing and commercializing innovative immuno-oncology and precision medicines to address the unmet medical needs of cancer patients in China and worldwide. Established in 2015, CStone has assembled a world-class management team with extensive experience in innovative drug development, clinical research, and commercialization. The company has built an oncology-focused pipeline of 15 drug candidates with a strategic emphasis on immuno-oncology combination therapies. Currently, five late-stage candidates are at pivotal trials. With an experienced team, a rich pipeline, a robust clinical development-driven business model and substantial funding, CStone’s vision is to become globally recognized as a leading Chinese biopharmaceutical company by bringing innovative oncology therapies to cancer patients worldwide.

For more information about CStone Pharmaceuticals, please visit: www.cstonepharma.com.

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