Study Overview

This is a multi-center, randomized, double-blind, placebo-controlled, event-driven, Phase 3 study to compare the efficacy, safety, and tolerability of nirogacestat and placebo in adult participants with progressing DT/AF. This study will consist of 2 phases, a double-blind and an optional open-label extension (OLE) phase. Participants will be screened up to 28 days prior to the first dose of study treatment (nirogacestat or placebo) in the double-blind phase and eligibility will be based on the inclusion and exclusion criteria. Approximately 135 participants will be screened (assessed for eligibility) to achieve 118 participants randomly assigned (1:1) to study treatment (placebo or nirogacestat). It is estimated that 51 observed progression events will be needed to meet the primary PFS analysis.

Study Eligibility

Inclusion Criteria

Participant must be at least 18 years of age at the time of signing the informed consent.

Type of Participant and Disease Characteristics

Participant has histologically confirmed DT/AF (by local pathologist prior to informed consent) that has progressed by ≥ 20% as measured by RECIST v1.1 within 12 months of the screening visit scan.

Participant has:

a. Treatment naïve, measurably progressing DT/AF that is deemed not amenable to surgery without the risk of significant morbidity;


b. Recurrent, measurably progressing DT/AF following at least one line of therapy;


c. Refractory, measurably progressing DT/AF following at least one line of therapy.

Participant has a DT/AF tumor where continued progressive disease will not result in immediate significant risk to the participant.

Participant agrees to provide archival or new tumor tissue for re-confirmation of disease. If participant is currently being treated with any therapy for the treatment of DT/AF, this must be completed at least 28 days (or 5 half-lives, whichever is longer) prior to first dose of study treatment. All toxicities from prior therapy must be resolved to ≤ Grade 1 or clinical baseline.

Participants who are receiving chronic nonsteroidal anti-inflammatory drugs (NSAIDs) as treatment for conditions other than DT/AF must be receiving them prior to the documented DT/AF progressive disease and on a stable dose for at least 28 days prior to the first dose of study treatment.

Participant has an Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 at screening.

Participant has adequate organ and bone marrow function as defined by the following screening laboratory values:

a. Absolute neutrophil count ≥ 1500 cells/μL;

b. Platelets ≥ 100,000μL;

c. Hemoglobin ≥ 9 g/dL;

d. Total bilirubin ≤ 1.5 × upper limit of normal (ULN) (isolated bilirubin > 1.5 x ULN is acceptable if bilirubin is fractionated and direct bilirubin < 35%); e. Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase)/alanine aminotransferase (ALT) (serum glutamic pyruvate transaminase) ≤ 2 × ULN; and

f. Serum creatinine ≤ 1.5 × ULN or if creatinine > 1.5 × ULN then calculated creatinine clearance must be ≥ 60 mL/min (using the Cockcroft-Gault formula); Participant can swallow tablets and has no gastrointestinal conditions affecting absorption.

Male or Female

Contraceptive use by men or women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.

a. Male participants:

Male participants are eligible to participate if they agree to the following during the treatment period and for at least 90 days after the last dose of study treatment:

Refrain from donating sperm;

PLUS either:

Be abstinent from sexual intercourse as their preferred and usual lifestyle (abstinent on a long term and persistent basis) and agree to remain abstinent;


Must agree to use a male condom when having sexual intercourse with women of childbearing potential (WOCBP).

b. Female participants:

A female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies:

Is not of childbearing potential


Is of childbearing potential but is abstinent or using 1 highly effective contraceptive method, during the treatment period and until 6 months after the last dose of study treatment. A second method of contraception is required if the participant is using hormonal contraception, as coadministration with nirogacestat may alter the plasma concentrations of hormonal contraceptives resulting in reduced efficacy. Additionally, the participant agrees not to harvest or donate eggs (ova, oocytes) for the purpose of reproduction during the treatment period and for at least 6 months after the last dose of active study treatment. The investigator should evaluate the effectiveness of the contraceptive method in relationship to the first dose of study treatment.

A WOCBP must have a negative serum pregnancy test result at screening and a negative urine pregnancy test result at the baseline visit prior to the first dose of study treatment.

Exclusion Criteria:

Participants are excluded from the double-blind phase if any of the following criteria apply:

Medical Conditions Participant has known malabsorption syndrome or preexisting gastrointestinal conditions that may impair absorption of nirogacestat (e.g., gastric bypass, lap band, or other gastric procedures that would alter absorption); delivery of nirogacestat via nasogastric tube or gastrostomy tube is not allowed.

Participant has experienced any of the following within 6 months of signing informed consent:

  • clinically significant cardiac disease (New York Heart Association Class III or IV);
  • myocardial infarction;
  • severe/unstable angina;
  • coronary/peripheral artery bypass graft;
  • symptomatic congestive heart failure;
  • cerebrovascular accident;
  • transient ischemic attack; or
  • symptomatic pulmonary embolism.
  • Participant has abnormal QT interval corrected by Fridericia’s formula (> 450 msec for male participants, > 470 msec for female participants, or > 480 msec for participants with bundle branch block) after electrolytes have been corrected (triplicate ECG readings, done approximately 2-3 minutes apart and averaged) at screening. Participant is using concomitant medications that are known to prolong the QT/QTcF interval including Class Ia (e.g., quinidine, procainamide, disopromide) and Class III (e.g., dofetilide, ibutilide, sotalol) antiarrhythmics at the time of informed consent. Nonantiarrhythmic medications which may prolong the QT/QTcF interval are allowed provided the participant does not have additional risk factors for Torsades de Pointes (TdP).

Participant has congenital long QT syndrome.

Participant has a history of additional risk factors for Torsades de Pointes (TdP) (e.g., heart failure, hypokalemia, family history of Long QT Syndrome).

Participant has had lymphoma, leukemia, or any malignancy within the past 5 years at the time of informed consent, except for any locally recurring cancer that has been treated curatively (e.g., resected basal or squamous cell skin cancer, superficial bladder cancer, carcinoma in situ of the cervix or breast), with no evidence of metastatic disease for 3 years at the time of informed consent.

Participant has current or chronic history of liver disease or known hepatic or biliary abnormalities (except for Gilbert’s syndrome or asymptomatic gallstones).

Prior/Concomitant Therapy

Participant previously received or is currently receiving therapy with GS inhibitors or anti-Notch antibody therapy.

Participant is currently using any treatment for DT/AF including tyrosine kinase inhibitors (TKIs), NSAIDs (chronic daily use) or any investigational treatment 28 days (or 5 half-lives, whichever is longer) prior to the first dose of study treatment.


Participant has started any treatment for DT/AF after the documented DT/AF progressive disease.

Participant is currently using or anticipates using food or drugs that are known strong/moderate cytochrome P450 3A4 (CYP3A4) inhibitors, or strong CYP3A inducers within 14 days prior to the first dose of study treatment.

Prior/Concurrent Clinical Study Experience

Participant is currently enrolled or was enrolled within 28 days of first dose of study treatment in another clinical study with any investigational drug or device. Participation in observational studies may be permitted with prior approval from the medical monitor/sponsor.

Diagnostic assessments

Participant has a positive human immunodeficiency virus antibody test. Participant has presence of Hepatitis B surface antigen at screening. Participant has a positive Hepatitis C antibody or Hepatitis C ribonucleic acid (RNA) test result at screening or within 3 months prior to starting study treatment.

NOTE: Participants with positive Hepatitis C antibody due to prior resolved disease can be enrolled, only if a confirmatory negative Hepatitis C RNA test is obtained. Test is optional and participants with negative Hepatitis C antibody test are not required to also undergo Hepatitis C RNA testing.

Other Exclusions

Participant is unable to tolerate MRI or for whom MRI is contraindicated. Participant with active or chronic infection at the time of informed consent and during the screening period.

Participant has experienced other severe acute or chronic medical or psychiatric conditions, including recent (within 1 year of signing informed consent) or active suicidal ideation or behavior, or a laboratory abnormality that may increase the risk associated with study participation or study treatment administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the participant inappropriate for entry into this study.

Participant has known hypersensitivity to the active substance or to any of the excipients of nirogacestat or placebo.

Participant is unable to comply with study related procedures (including, but not limited to, the completion of electronic patient report outcomes (ePROs), or the ePRO questionnaires are not available in the participant’s preferred language)


For more information about this study, contact Catherine Redinger at 501-364-4290 ( or Suzy Hall at 501-364-4181 (