Blueprint Medicines Announces Positive Top-line Results from EXPLORER and PATHFINDER Trials of AYVAKIT™ (avapritinib) in Patients with Advanced Systemic Mastocytosis
SM is a rare, debilitating disease driven by the KIT D816V mutation in nearly all patients. Uncontrolled mast cell proliferation and activation may lead to life-threatening complications across the SM patient population. In advanced SM subtypes, the median OS is approximately 3.5 years in aggressive SM (ASM), approximately two years in SM with an associated hematologic neoplasm (SM-AHN) and less than six months in mast cell leukemia (MCL). AYVAKIT, an investigational precision therapy for the treatment of SM, is the only highly potent KIT D816V inhibitor that has been clinically validated in SM.
"New treatment options are urgently needed to address mast cell infiltration associated with advanced systemic mastocytosis, which often leads to extensive organ damage and poor survival despite existing therapeutic interventions," said
Top-line EXPLORER and PATHFINDER Trial Data
Across both trials, 85 patients were evaluable for response per the modified IWG-MRT-ECNM criteria (IWG criteria), including 44 patients treated with a starting dose of 200 mg QD. Top-line results are being reported as of a data cutoff date of
In the EXPLORER trial, 53 patients were response evaluable, with a median follow-up of 27.3 months. In EXPLORER, the ORR was 76 percent (95% CI: 62%, 86%), and 36 percent of patients had a CR/CRh. The median DOR was 38.3 months (95% CI: 21.7 months, not estimable). The median OS was not estimable (95% CI: 46.9 months, not estimable).
In a pre-specified interim analysis from the PATHFINDER trial, 32 patients were response evaluable, with a median follow-up of 10.4 months. The ORR was 75 percent (95% CI: 57%, 89%), and 19 percent of patients had a CR/CRh. In addition, the data showed that responses are continuing to deepen over time, at a rate consistent with the EXPLORER trial. The median DOR was not estimable (95% CI: not estimable, not estimable), and OS was not assessed due to the length of time patients have been enrolled in PATHFINDER. The top-line PATHFINDER results were based on a pre-planned analysis designed to assess the superiority of AYVAKIT versus the ORR per IWG criteria previously reported for the multi-kinase inhibitor midostaurin. The interim analysis achieved its primary endpoint with a p-value of p=0.0000000016.
In a pooled efficacy analysis from the 200 mg QD dose group, 44 patients were response evaluable, with a median follow-up of 10.4 months. In this group, the ORR was 68 percent, and 18 percent of patients had a CR/CRh.
Safety data were consistent with previously reported results, and no new signals were observed. AYVAKIT was generally well-tolerated with most adverse events (AEs) reported as Grade 1 or 2. In the EXPLORER and PATHFINDER trials, AYVAKIT demonstrated improved tolerability at a starting dose of 200 mg QD, compared to all doses. Across both trials, 8.1 percent of patients discontinued AYVAKIT due to treatment-related AEs.
Previously reported results from the EXPLORER trial showed that pre-existing severe thrombocytopenia, which occurs in approximately 10 to 15 percent of advanced SM patients based on
Conference Call Information
SM is a rare disease driven by the KIT D816V mutation. Uncontrolled proliferation and activation of mast cells result in chronic, severe and often unpredictable symptoms for patients across the spectrum of SM. The vast majority of those affected have non-advanced (indolent or smoldering) SM, with debilitating symptoms that lead to a profound, negative impact on quality of life. A minority of patients have advanced SM, which encompasses a group of high-risk SM subtypes including ASM, SM-AHN and MCL. In addition to mast cell activation symptoms, advanced SM is associated with organ damage due to mast cell infiltration and poor OS.
Debilitating symptoms associated with SM, including anaphylaxis, maculopapular rash, pruritis, brain fog, fatigue and bone pain, often persist despite treatment with a number of symptomatic therapies. Patients often live in fear of attacks, have limited ability to work or perform daily activities, or isolate themselves to protect against unpredictable triggers.
Currently, there are no approved therapies that selectively inhibit D816V mutant KIT. A multi-kinase inhibitor, midostaurin, is approved for the treatment of advanced SM and has shown an ORR of 28 percent per IWG criteria, with ORR defined as complete remission, partial remission or clinical improvement.
About AYVAKIT (avapritinib)
AYVAKIT (avapritinib) is a kinase inhibitor approved by the FDA for the treatment of adults with unresectable or metastatic gastrointestinal stromal tumor (GIST) harboring a PDGFRA exon 18 mutation, including PDGFRA D842V mutations. For more information, visit www.AYVAKIT.com.
AYVAKIT is not approved for the treatment of any other indication, including SM, in the
AYVAKIT is currently being evaluated in two ongoing, registrational clinical trials for advanced SM: the EXPLORER trial (ClinicalTrials.gov Identifier: NCT02561988) and the PATHFINDER trial (ClinicalTrials.gov Identifier: NCT03580655).
The EXPLORER trial is an open-label, single-arm trial designed to identify the recommended Phase 2 dose and demonstrate proof-of-concept in patients with advanced SM. Key trial endpoints include ORR, DOR, quantitative measures of mast cell burden, patient-reported outcomes and safety. The EXPLORER trial has completed patient enrollment.
The PATHFINDER trial is an open-label, single-arm registration-enabling trial designed to confirm the clinical activity of AYVAKIT in patients with advanced SM. Key trial endpoints include ORR, DOR, quantitative measures of mast cell burden, patient-reported outcomes and safety. Patient enrollment is ongoing in the PATHFINDER trial.
Patients and physicians interested in SM clinical trials can contact the
Blueprint Medicines is a precision therapy company striving to improve human health. With a focus on genomically defined cancers, rare diseases and cancer immunotherapy, we are developing transformational medicines rooted in our leading expertise in protein kinases, which are proven drivers of disease. Our uniquely targeted, scalable approach empowers the rapid design and development of new treatments and increases the likelihood of clinical success. We have two FDA-approved precision therapies and are currently advancing multiple investigational medicines in clinical development, along with a number of research programs. For more information, visit www.BlueprintMedicines.com and follow us on Twitter (@BlueprintMeds) and LinkedIn.
Cautionary Note Regarding Forward-Looking Statements
This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including, without limitation, statements regarding plans, timelines and expectations for interactions with the FDA and other regulatory authorities; plans and timelines for submitting an sNDA to the FDA for AYVAKIT for the treatment of advanced SM; expectations regarding the potential benefits of AYVAKIT in treating patients with SM; and
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