Blueprint Medicines Data Presented at 62nd ASH Annual Meeting and Exposition Highlight Broad Commitment to Advance Patient Care in Systemic Mastocytosis

CAMBRIDGE, Mass., Dec. 7, 2020 /PRNewswire/ -- Blueprint Medicines Corporation (NASDAQ: BPMC), a precision therapy company focused on genomically defined cancers, rare diseases and cancer immunotherapy, today announced data from six oral and poster presentations highlighted at the virtual 62^nd American Society of Hematology (ASH) Annual Meeting and Exposition. These data demonstrate the company's broad efforts to understand the disease burden, accelerate the diagnosis and transform the treatment of systemic mastocytosis (SM).

"The medical needs in systemic mastocytosis are significant and urgent, and our presentations at the ASH annual meeting demonstrate our efforts to help address these challenges in collaboration with disease experts and the patient community," said Andy Boral, M.D., Ph.D., Chief Medical Officer at Blueprint Medicines. "AYVAKIT, an investigational precision therapy for the treatment of SM, is the only potent KIT D816V inhibitor to show a high complete remission rate in advanced SM, as well as improvements in mast cell burden, disease symptoms and quality of life in non-advanced SM. With this foundation of unprecedented clinical data, we continue to build momentum toward bringing AYVAKIT to patients. Later this month, we plan to submit a supplemental new drug application to the FDA for AYVAKIT for advanced SM, and we continue to globally enroll the registrational PIONEER trial for non-advanced SM."

Pure Pathologic Response (PPR) Measures Reduction and Elimination of Mast Cell Burden in Advanced SM, and Significantly Correlates with Improved Overall Survival (OS)

The IWG-MRT-ECNM response criteria (IWG criteria) are the current clinical and regulatory standard for evaluating treatment response in patients with advanced SM, and are primarily based on the resolution of organ damage. With the development of a potent and selective KIT D816V inhibitor, new PPR criteria were established by global SM experts in collaboration with Blueprint Medicines to measure objective reductions and elimination of neoplastic mast cells at the pathological and molecular level. These assessments are used in routine clinical practice, making the criteria more practical in the real-world setting.

In the Phase 1 EXPLORER trial, 53 patients with advanced SM were treated with AYVAKIT and evaluable for response per modified IWG criteria as of a data cutoff of May 27, 2020. The overall response rate (ORR) was 75 percent, and the rate of complete remission with full or partial hematologic recovery (CR/CRh) was 36 percent per modified IWG criteria, consistent with previously reported data. In the same population, the ORR was 77 percent and the CR/CRh rate was 47 percent per PPR criteria. Twenty-five percent of patients had a molecular CR/CRh, with no measurable evidence of residual KIT D816V mutation in the blood or bone marrow. Importantly, patients with a PPR response at six months had significantly improved OS (p=0.013). In the EXPLORER trial, AYVAKIT was generally well-tolerated, and safety data were consistent with previously reported results.

"For patients with advanced systemic mastocytosis, our primary treatment goals are to rapidly reduce their mast cell burden, improve quality of life, and importantly, prolong survival," said Jason Gotlib, M.D., M.S., Professor of Medicine, Hematology, at the Stanford Cancer Institute and an investigator on the EXPLORER trial. "To advance clinical research, it is important to establish objective measures of response that correlate with clinically significant outcomes and can be broadly incorporated into medical practice. The development of pure pathologic response criteria is a promising approach for assessing treatment response to avapritinib and its impact on survival, and clinically validates the role of KIT D816V inhibition in advanced mast cell disease."

Highly Sensitive Blood-Based Droplet Digital Polymerase Chain Reaction (ddPCR) Test Detects KIT D816V Mutation in 95% of Patients

Registry data have shown a median delay of nine years from symptom onset to diagnosis in patients with non-advanced SM,¹ highlighting the need for new diagnostic tools.

In Part 1 of the PIONEER trial of AYVAKIT in patients with non-advanced SM, the sensitivity of ddPCR and next-generation sequencing (NGS) KIT D816V testing was evaluated. As of a data cutoff of December 27, 2019, in all 39 enrolled patients who received testing, a blood-based ddPCR test identified the KIT D816V mutation in 95 percent of patients, compared to 28 percent of patients evaluated by an NGS test performed on bone marrow aspirates. In addition, the ddPCR-based KIT D816V test was more sensitive compared to measurements of serum tryptase (77 percent) and bone marrow mast cells (90 percent) using standard World Health Organization diagnostic criteria. These results highlight the clinical value of blood-based, ddPCR-based KIT D816V testing as a confirmatory diagnostic tool to facilitate identification of patients with non-advanced SM, and a non-invasive screening tool for identifying patients with suspected advanced SM that requires a confirmatory bone marrow biopsy.

SM Patients Reported Worse Physical Functioning and Mental Health Compared to Historical Data for Patients with Lung and Colorectal Cancer

SM is characterized by unpredictable, severe and life-threatening complications despite best supportive care. To better understand the burden of disease, Blueprint Medicines is collaborating with clinical experts on the TouchStone survey, a study of adults with SM (n=56), and allergists/immunologists (n=60) and hematologists/oncologists (n=59) who care for patients with SM.

The TouchStone survey showed that SM symptoms have a profound impact on patients' daily functioning, mental health, and ability to work or perform usual activities. Compared to prior research on colorectal and lung cancer patients, participants reported worse physical functioning and mental health based on the 12-item Short Form Survey (SF-12) questionnaire, a valid and widely used health status measure. More than half of patients (54 percent) reported reduced hours at work, and 32 percent filed for medical disability due to their SM. Respondents cited the use of multiple over-the-counter and prescription medications, and frequent visits to physician specialists and the emergency department to manage their SM. In a one-year period, 30 percent of participants reported going to the emergency room at least once for anaphylaxis.

Healthcare providers broadly recognized the high disease burden in SM. A majority reported that non-advanced SM patients under their care feel depressed or discouraged, and limit their activities due to pain or discomfort. For healthcare providers, the most important treatment goals for advanced and non-advanced SM are improved progression-free survival and OS, and better quality of life.

Copies of Blueprint Medicines data presentations from the ASH annual meeting are available in the "Science—Publications and Presentations" section of the company's website at www.BlueprintMedicines.com.

About SM

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 aggressive SM, SM with an associated hematologic neoplasm and mast cell leukemia. 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.

About AYVAKIT (avapritinib)

AYVAKIT (avapritinib) is a kinase inhibitor approved by the U.S. Food and Drug Administration (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. This medicine is approved in Europe under the brand name AYVAKYT® for the treatment of adults with unresectable or metastatic GIST harboring the PDGFRA D842V mutation.

AYVAKIT/AYVAKYT is not approved for the treatment of any other indication, including SM, in the U.S. by the FDA or in Europe by the European Commission, or for any indication in any other jurisdiction by any other health authority.

Blueprint Medicines is developing AYVAKIT globally for the treatment of advanced and indolent SM. The FDA granted breakthrough therapy designation to AYVAKIT for the treatment of advanced SM, including the subtypes of aggressive SM, SM with an associated hematologic neoplasm and mast cell leukemia.

Blueprint Medicines has an exclusive collaboration and license agreement with CStone Pharmaceuticals for the development and commercialization of AYVAKIT in Mainland China, Hong Kong, Macau and Taiwan. Blueprint Medicines retains development and commercial rights for AYVAKIT in the rest of the world.

About Blueprint Medicines

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 approved precision therapies and are currently advancing multiple investigational medicines in clinical and pre-clinical development, along with a number of earlier-stage 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 a supplemental new drug application to the FDA for AYVAKIT for the treatment of advanced SM; expectations regarding the potential benefits of AYVAKIT in treating patients with SM; and Blueprint Medicines' strategy, goals and anticipated milestones, business plans and focus. The words "aim," "may," "will," "could," "would," "should," "expect," "plan," "anticipate," "intend," "believe," "estimate," "predict," "project," "potential," "continue," "target" and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Any forward-looking statements in this press release are based on management's current expectations and beliefs and are subject to a number of risks, uncertainties and important factors that may cause actual events or results to differ materially from those expressed or implied by any forward-looking statements contained in this press release, including, without limitation, risks and uncertainties related to the impact of the COVID-19 pandemic to Blueprint Medicines' business, operations, strategy, goals and anticipated milestones, including Blueprint Medicines' ongoing and planned research and discovery activities, ability to conduct ongoing and planned clinical trials, clinical supply of current or future drug candidates, commercial supply of current or future approved products, and launching, marketing and selling current or future approved products; Blueprint Medicines' ability and plans in establishing a commercial infrastructure, and successfully launching, marketing and selling current or future approved products, including AYVAKIT and GAVRETO™ (pralsetinib); Blueprint Medicines' ability to successfully expand the approved indications for AYVAKIT and GAVRETO or obtain marketing approval for AYVAKIT and GAVRETO in additional geographies in the future; the delay of any current or planned clinical trials or the development of Blueprint Medicines' current or future drug candidates; Blueprint Medicines' advancement of multiple early-stage efforts; Blueprint Medicines' ability to successfully demonstrate the safety and efficacy of its drug candidates and gain approval of its drug candidates on a timely basis, if at all; the pre-clinical and clinical results for Blueprint Medicines' drug candidates, which may not support further development of such drug candidates; actions of regulatory agencies, which may affect the initiation, timing and progress of clinical trials; Blueprint Medicines' ability to develop and commercialize companion diagnostic tests for its current and future drug candidates; and the success of Blueprint Medicines' current and future collaborations, partnerships or licensing arrangements, including Blueprint Medicines' global collaboration with Roche for the development and commercialization of GAVRETO. These and other risks and uncertainties are described in greater detail in the section entitled "Risk Factors" in Blueprint Medicines' filings with the Securities and Exchange Commission (SEC), including Blueprint Medicines' most recent Annual Report on Form 10-K, as supplemented by its most recent Quarterly Report on Form 10-Q and any other filings that Blueprint Medicines has made or may make with the SEC in the future. Any forward-looking statements contained in this press release represent Blueprint Medicines' views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date. Except as required by law, Blueprint Medicines explicitly disclaims any obligation to update any forward-looking statements. 

Reference

¹ Jennings SV, Slee VM, Zach, RM, et al. Patient Perceptions in Mast Cell Disorders. Immunol Allergy Clin North Am. 2018;38(3):505-525.

Trademarks

Blueprint Medicines, AYVAKIT, AYVAKYT, GAVRETO and associated logos are trademarks of Blueprint Medicines Corporation.

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