On August 22, 2018 Pfizer Inc. (NYSE:PFE) and Astellas Pharma Inc. (TSE:4503, President and CEO: Kenji Yasukawa, Ph.D., "Astellas") reported amendments to the protocols for two registrational Phase 3 trials, ARCHES and EMBARK, designed to evaluate the safety and efficacy of XTANDI (enzalutamide) in men with hormone-sensitive prostate cancer (HSPC) (Press release, Pfizer, AUG 22, 2018, https://www.pfizer.com/news/press-release/press-release-detail/pfizer_and_astellas_amend_clinical_research_protocols_for_two_phase_3_trials_of_enzalutamide_in_patients_with_hormone_sensitive_prostate_cancer [SID1234529035]). These amendments accelerate timelines for the anticipated primary completion dates of both trials.

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ARCHES is a randomized Phase 3 study evaluating the efficacy and safety of enzalutamide plus androgen deprivation therapy (ADT) versus ADT alone in metastatic HSPC patients. The primary endpoint of the trial is radiographic progression-free survival (rPFS). Changes to the protocol include revision of the planned analyses of the primary and secondary endpoints. Enrollment was completed earlier this year. The companies now anticipate the primary completion date for the ARCHES clinical trial to be in late 2018. The previously expected primary completion date was April 2020.

Revisions were also made to the protocol for EMBARK, a randomized Phase 3 study of enzalutamide plus leuprolide, enzalutamide monotherapy, and leuprolide alone in men with high-risk non-metastatic HSPC. The primary endpoint of the trial is metastasis-free survival (MFS). The main purpose of the amendment is to revise the planned analyses of the primary and several secondary endpoints, which reduced the target sample size. Enrollment was completed earlier this year. With these changes, the estimated primary completion date for the EMBARK clinical trial is mid-2020. Previously, the expected primary completion date for EMBARK was March 2021.

"We continually strive to design and implement clinical trials that bring innovations to people with the greatest need," said Steven Benner, M.D., senior vice president and global therapeutic area head, Oncology Development, Astellas. "With the amendments to ARCHES and EMBARK, we will be able to evaluate the potential of XTANDI for men with hormone-sensitive prostate cancer sooner, including for those with non-metastatic disease in which there are no currently approved oral treatment options."

"With a large body of evidence demonstrating the activity of XTANDI in men with castrate-resistant prostate cancer, ARCHES and EMBARK are designed to extend the evaluation of XTANDI to men with hormone-sensitive prostate cancer," said Mace Rothenberg, M.D., chief development officer, Oncology, Pfizer Global Product Development. "Our goal is to build upon the body of clinical evidence for enzalutamide in an effort to help address the unmet needs of an even broader spectrum of prostate cancer patients."

XTANDI is approved by the U.S. Food and Drug Administration for the treatment of castration-resistant prostate cancer.

Details regarding ARCHES (NCT02677896) and EMBARK (NCT02319837) are available on ClinicalTrials.gov.

About XTANDI (enzalutamide) capsules XTANDI (enzalutamide) is an androgen receptor inhibitor indicated for the treatment of patients with castration-resistant prostate cancer.

Important Safety Information for XTANDI

Warnings and Precautions
Seizure occurred in 0.4% of patients receiving XTANDI in clinical studies. In a study of patients with predisposing factors for seizure, 2.2% of XTANDI-treated patients experienced a seizure. Patients in the study had one or more of the following pre-disposing factors: use of medications that may lower the seizure threshold; history of traumatic brain or head injury, cerebrovascular accident or transient ischemic attack, Alzheimer’s disease, meningioma, or leptomeningeal disease from prostate cancer, unexplained loss of consciousness within the last 12 months, history of seizure, presence of a space occupying lesion of the brain, history of arteriovenous malformation, or history of brain infection. It is unknown whether anti-epileptic medications will prevent seizures with XTANDI. Advise patients of the risk of developing a seizure while taking XTANDI and of engaging in any activity where sudden loss of consciousness could cause serious harm to themselves or others. Permanently discontinue XTANDI in patients who develop a seizure during treatment.

Posterior Reversible Encephalopathy Syndrome (PRES) In post approval use, there have been reports of PRES in patients receiving XTANDI. PRES is a neurological disorder which can present with rapidly evolving symptoms including seizure, headache, lethargy, confusion, blindness, and other visual and neurological disturbances, with or without associated hypertension. A diagnosis of PRES requires confirmation by brain imaging, preferably MRI. Discontinue XTANDI in patients who develop PRES.

Hypersensitivity reactions, including edema of the face (0.5%), tongue (0.1%), or lip (0.1%) have been observed with XTANDI in clinical trials. Pharyngeal edema has been reported in post-marketing cases. Advise patients who experience any symptoms of hypersensitivity to temporarily discontinue XTANDI and promptly seek medical care. Permanently discontinue XTANDI for serious hypersensitivity reactions.

Ischemic Heart Disease In the placebo-controlled clinical studies, ischemic heart disease occurred more commonly in patients on the XTANDI arm compared to patients on the placebo arm (2.7% vs 1.2%). Grade 3-4 ischemic events occurred in 1.2% of patients on XTANDI versus 0.5% on placebo. Ischemic events led to death in 0.4% of patients on XTANDI compared to 0.1% on placebo. Monitor for signs and symptoms of ischemic heart disease. Optimize management of cardiovascular risk factors, such as hypertension, diabetes, or dyslipidemia. Discontinue XTANDI for Grade 3-4 ischemic heart disease.

Falls and Fractures In the placebo-controlled clinical studies, falls occurred in 10% of patients treated with XTANDI compared to 4% of patients treated with placebo. Fractures occurred in 8% of patients treated with XTANDI and in 3% of patients treated with placebo. Evaluate patients for fracture and fall risk. Monitor and manage patients at risk for fractures according to established treatment guidelines and consider use of bone-targeted agents.

Embryo-Fetal Toxicity Safety and efficacy of XTANDI have not been established in females. XTANDI can cause fetal harm and loss of pregnancy when administered to a pregnant female. Advise males with female partners of reproductive potential to use effective contraception during treatment with XTANDI and for 3 months after the last dose of XTANDI. XTANDI should not be handled by females who are or may become pregnant.

Adverse Reactions
The most common adverse reactions (≥ 10%) that occurred more frequently (≥ 2% over placebo) in the XTANDI patients from the randomized placebo-controlled trials were asthenia/fatigue, decreased appetite, hot flush, arthralgia, dizziness/vertigo, hypertension, headache and weight decreased. In the bicalutamide-controlled study, the most common adverse reactions (≥ 10%) reported in XTANDI patients were asthenia/fatigue, back pain, musculoskeletal pain, hot flush, hypertension, nausea, constipation, diarrhea, upper respiratory tract infection, and weight loss.

In the placebo-controlled study of metastatic CRPC (mCRPC) patients taking XTANDI who previously received docetaxel, Grade 3 and higher adverse reactions were reported among 47% of XTANDI patients and 53% of placebo patients. Discontinuations due to adverse events were reported for 16% of XTANDI patients and 18% of placebo patients. In the placebo-controlled study of chemotherapy-naïve mCRPC patients, Grade 3-4 adverse reactions were reported in 44% of XTANDI patients and 37% of placebo patients. Discontinuations due to adverse events were reported for 6% of both study groups. In the placebo-controlled study of non-metastatic CRPC (nmCRPC) patients, Grade 3 or higher adverse reactions were reported in 31% of XTANDI patients and 23% of placebo patients. Discontinuations with an adverse event as the primary reason were reported for 9% of XTANDI patients and 6% of placebo patients. In the bicalutamide-controlled study of chemotherapy-naïve mCRPC patients, Grade 3-4 adverse reactions were reported in 39% of XTANDI patients and 38% of bicalutamide patients. Discontinuations with an AE as the primary reason were reported for 8% of XTANDI patients and 6% of bicalutamide patients.

Lab Abnormalities: In the two placebo-controlled trials in patients with mCRPC, Grade 1-4 neutropenia occurred in 15% of XTANDI patients (1% Grade 3-4) and 6% of placebo patients (0.5% Grade 3-4). In the placebo-controlled trial in patients with nmCRPC, Grade 1-4 neutropenia occurred in 8% of patients receiving XTANDI (0.5% Grade 3-4) and in 5% of patients receiving placebo (0.2% Grade 3-4).

Hypertension: In the two placebo-controlled trials in patients with mCRPC, hypertension was reported in 11% of XTANDI patients and 4% of placebo patients. Hypertension led to study discontinuation in <1% of patients in each arm. In the placebo-controlled trial in patients with nmCRPC, hypertension was reported in 12% of patients receiving XTANDI and 5% of patients receiving placebo.

Drug Interactions
Effect of Other Drugs on XTANDI Avoid strong CYP2C8 inhibitors, as they can increase the plasma exposure to XTANDI. If co-administration is necessary, reduce the dose of XTANDI.

Avoid strong CYP3A4 inducers as they can decrease the plasma exposure to XTANDI. If co-administration is necessary, increase the dose of XTANDI.

Effect of XTANDI on Other Drugs Avoid CYP3A4, CYP2C9, and CYP2C19 substrates with a narrow therapeutic index, as XTANDI may decrease the plasma exposures of these drugs. If XTANDI is co-administered with warfarin (CYP2C9 substrate), conduct additional INR monitoring.