Regadenoson Injection

Regadenoson is an A2A adenosine receptor agonist that is a coronary vasodilator [see CLINICAL PHARMACOLOGY]. Regadenoson is chemically described as adenosine, 2-[4[(methylamino)carbonyl]-1H-pyrazol-1-yl]-, monohydrate. Its structural formula is:

The molecular formula for regadenoson is C15H18N8O5 • H2O and its molecular weight is 408.37. LEXISCAN is a sterile, nonpyrogenic solution for intravenous injection. The solution is clear and colorless. Each 1 mL in the 5 mL pre-filled syringe contains 0.084 mg of regadenoson monohydrate, corresponding to 0.08 mg regadenoson on an anhydrous basis, 10.9 mg dibasic sodium phosphate dihydrate or 8.7 mg dibasic sodium phosphate anhydrous, 5.4 mg monobasic sodium phosphate monohydrate, 150 mg propylene glycol, 1 mg edetate disodium dihydrate, and Water for Injection, with pH between 6.3 and 7.7.

Mechanism Of Action

Regadenoson is a low affinity agonist (Ki ≈ 1.3 μM) for the A2A adenosine receptor, with at least 10-fold lower affinity for the A1 adenosine receptor (Ki > 16.5 μM), and weak, if any, affinity for the A2B and A3 adenosine receptors. Activation of the A2A adenosine receptor by regadenoson produces coronary vasodilation and increases coronary blood flow (CBF).

Pharmacodynamics

Coronary Blood Flow LEXISCAN causes a rapid increase in CBF which is sustained for a short duration. In patients undergoing coronary catheterization, pulsed-wave Doppler ultrasonography was used to measure the average peak velocity (APV) of coronary blood flow before and up to 30 minutes after administration of regadenoson (0.4 mg, intravenously). Mean APV increased to greater than twice baseline by 30 seconds and decreased to less than twice the baseline level within 10 minutes [see Pharmacokinetics].

Myocardial uptake of the radiopharmaceutical is proportional to CBF. Because LEXISCAN increases blood flow in normal coronary arteries with little or no increase in stenotic arteries, LEXISCAN causes relatively less uptake of the radiopharmaceutical in vascular territories supplied by stenotic arteries. MPI intensity after LEXISCAN administration is therefore greater in areas perfused by normal relative to stenosed arteries.

Aminophylline (100 mg, administered by slow intravenous injection over 60 seconds) injected 1 minute after 0.4 mg LEXISCAN in patients undergoing cardiac catheterization, was shown to shorten the duration of the coronary blood flow response to LEXISCAN as measured by pulsed-wave Doppler ultrasonography [see OVERDOSAGE].

Ingestion of caffeine decreases the ability to detect reversible ischemic defects. In a placebo-controlled, parallel group clinical study, patients with known or suspected myocardial ischemia received a baseline rest/stress MPI followed by a second stress MPI. Patients received caffeine or placebo 90 minutes before the second LEXISCAN stress MPI. Following caffeine administration (200 or 400 mg), the mean number of reversible defects identified was reduced by approximately 60%. This decrease was statistically significant [see DRUG INTERACTIONS and PATIENT INFORMATION].

In clinical studies, the majority of patients had an increase in heart rate and a decrease in blood pressure within 45 minutes after administration of LEXISCAN. Maximum hemodynamic changes after LEXISCAN and ADENOSCAN in Studies 1 and 2 are summarized in Table 5.

Table 5 : Hemodynamic Effects in Studies 1 and 2

In a clinical study, LEXISCAN was administered for MPI following inadequate exercise stress. More patients with LEXISCAN administration three minutes following inadequate exercise stress had an increase in heart rate and a decrease in systolic blood pressure compared with LEXISCAN administered at rest. The changes were not associated with any clinically significant adverse reactions. Maximum hemodynamic changes are presented in Table 6.

Table 6 : Hemodynamic Effects in Inadequate Exercise Stress Study

The A2B and A3 adenosine receptors have been implicated in the pathophysiology of bronchoconstriction in susceptible individuals (i.e., asthmatics). In in vitro studies, regadenoson has not been shown to have appreciable binding affinity for the A2B and A3 adenosine receptors.

In a randomized, placebo-controlled clinical trial of 999 patients with a diagnosis, or risk factors for, coronary artery disease and concurrent asthma or COPD, the incidence of respiratory adverse reactions (dyspnea, wheezing) was greater with LEXISCAN compared to placebo. Moderate (2.5%) or severe ( < 1%) respiratory reactions were observed more frequently in the LEXISCAN group compared to placebo [see ADVERSE REACTIONS].

Pharmacokinetics

In healthy subjects, the regadenoson plasma concentration-time profile is multi-exponential in nature and best characterized by 3-compartment model. The maximal plasma concentration of regadenoson is achieved within 1 to 4 minutes after injection of LEXISCAN and parallels the onset of the pharmacodynamic response. The half-life of this initial phase is approximately 2 to 4 minutes. An intermediate phase follows, with a half-life on average of 30 minutes coinciding with loss of the pharmacodynamic effect. The terminal phase consists of a decline in plasma concentration with a half-life of approximately 2 hours [see Pharmacodynamics]. Within the dose range of 0.3-20 μg/kg in healthy subjects, clearance, terminal half-life or volume of distribution do not appear dependent upon the dose.

A population pharmacokinetic analysis including data from subjects and patients demonstrated that regadenoson clearance decreases in parallel with a reduction in creatinine clearance and clearance increases with increased body weight. Age, gender, and race have minimal effects on the pharmacokinetics of regadenoson.

Specific Populations

Renally Impaired Patients: The disposition of regadenoson was studied in 18 patients with various degrees of renal function and in 6 healthy subjects. With increasing renal impairment, from mild (CLcr 50 to < 80 mL/min) to moderate (CLcr 30 to < 50 mL/min) to severe renal impairment (CLcr < 30 mL/min), the fraction of regadenoson excreted unchanged in urine and the renal clearance decreased, resulting in increased elimination half-lives and AUC values compared to healthy subjects (CLcr ≥ 80 mL/min). However, the maximum observed plasma concentrations as well as volumes of distribution estimates were similar across the groups. The plasma concentration-time profiles were not significantly altered in the early stages after dosing when most pharmacologic effects are observed. No dose adjustment is needed in patients with renal impairment.

Patients with End Stage Renal Disease: The pharmacokinetics of regadenoson in patients on dialysis has not been assessed; however, in an in vitro study regadenoson was found to be dialyzable.

Hepatically Impaired Patients: The influence of hepatic impairment on the pharmacokinetics of regadenoson has not been evaluated. Because greater than 55% of the dose is excreted in the urine as unchanged drug and factors that decrease clearance do not affect the plasma concentration in the early stages after dosing when clinically meaningful pharmacologic effects are observed, no dose adjustment is needed in patients with hepatic impairment.

Geriatric Patients: Based on a population pharmacokinetic analysis, age has a minor influence on the pharmacokinetics of regadenoson. No dose adjustment is needed in elderly patients.

The metabolism of regadenoson is unknown in humans. Incubation with rat, dog, and human liver microsomes as well as human hepatocytes produced no detectable metabolites of regadenoson.

In healthy volunteers, 57% of the regadenoson dose is excreted unchanged in the urine (range 1977%), with an average plasma renal clearance around 450 mL/min, i.e., in excess of the glomerular filtration rate. This indicates that renal tubular secretion plays a role in regadenoson elimination.

Animal Toxicology And/Or Pharmacology

Minimal cardiomyopathy (myocyte necrosis and inflammation) was observed in rats following single-dose administration of regadenoson. Increased incidence of minimal cardiomyopathy was observed on day 2 in males at doses of 0.08, 0.2 and 0.8 mg/kg (1/5, 2/5, and 5/5) and in females (2/5) at 0.8 mg/kg. In a separate study in male rats, the mean arterial pressure was decreased by 30 to 50% of baseline values for up to 90 minutes at regadenoson doses of 0.2 and 0.8 mg/kg, respectively. No cardiomyopathy was noted in rats sacrificed 15 days following single administration of regadenoson. The mechanism of the cardiomyopathy induced by regadenoson was not elucidated in this study but was associated with the hypotensive effects of regadenoson. Profound hypotension induced by vasoactive drugs is known to cause cardiomyopathy in rats.

Intravenous administration of LEXISCAN to rabbits resulted in perivascular hemorrhage, vein vasculitis, inflammation, thrombosis and necrosis, with inflammation and thrombosis persisting through day 8 (last observation day). Perivascular administration of LEXISCAN to rabbits resulted in hemorrhage, inflammation, pustule formation and epidermal hyperplasia, which persisted through day 8 except for the hemorrhage which resolved. Subcutaneous administration of LEXISCAN to rabbits resulted in hemorrhage, acute inflammation, and necrosis; on day 8 muscle fiber regeneration was observed.

Clinical Studies

The efficacy and safety of LEXISCAN were determined relative to ADENOSCAN in two randomized, double-blind studies (Studies 1 and 2) in 2,015 patients with known or suspected coronary artery disease who were indicated for pharmacologic stress MPI. A total of 1,871 of these patients had images considered valid for the primary efficacy evaluation, including 1,294 (69%) men and 577 (31%) women with a median age of 66 years (range 26-93 years of age). Each patient received an initial stress scan using ADENOSCAN (6-minute infusion using a dose of 0.14 mg/kg/min, without exercise) with a radionuclide gated SPECT imaging protocol. After the initial scan, patients were randomized to either LEXISCAN or ADENOSCAN, and received a second stress scan with the same radionuclide imaging protocol as that used for the initial scan. The median time between scans was 7 days (range of 1-104 days).

The most common cardiovascular histories included hypertension (81%), CABG, PTCA or stenting (51%), angina (63%), and history of myocardial infarction (41%) or arrhythmia (33%); other medical history included diabetes (32%) and COPD (5%). Patients with a recent history of serious uncontrolled ventricular arrhythmia, myocardial infarction, or unstable angina, a history of greater than first-degree AV block, or with symptomatic bradycardia, sick sinus syndrome, or a heart transplant were excluded. A number of patients took cardioactive medications on the day of the scan, including β-blockers (18%), calcium channel blockers (9%), and nitrates (6%). In the pooled study population, 68% of patients had 0-1 segments showing reversible defects on the initial scan, 24% had 2-4 segments, and 9% had ≥ 5 segments.

Comparison of the images obtained with LEXISCAN to those obtained with ADENOSCAN was performed as follows. Using the 17-segment model, the number of segments showing a reversible perfusion defect was calculated for the initial ADENOSCAN study and for the randomized study obtained using LEXISCAN or ADENOSCAN. The agreement rate for the image obtained with LEXISCAN or ADENOSCAN relative to the initial ADENOSCAN image was calculated by determining how frequently the patients assigned to each initial ADENOSCAN category (0-1, 2-4, 5-17 reversible segments) were placed in the same category with the randomized scan. The agreement rates for LEXISCAN and ADENOSCAN were calculated as the average of the agreement rates across the three categories determined by the initial scan. Studies 1 and 2 each demonstrated that LEXISCAN is similar to ADENOSCAN in assessing the extent of reversible perfusion abnormalities (Table 7).

Table 7 : Agreement Rates in Studies 1 and 2

The efficacy and safety of LEXISCAN administered 3 minutes (Group 1) or 1 hour (Group 2) following inadequate exercise stress were evaluated in an open-label randomized, multi-center, non-inferiority study. Adequate exercise was defined as ≥ 85% maximum predicted heart rate and ≥ 5 METS. SPECT MPI was performed 60-90 minutes after LEXISCAN administration in each group (MPI 1). Patients returned 1-14 days later to undergo a second stress MPI with LEXISCAN without exercise (MPI 2).

All patients were referred for evaluation of coronary artery disease. Of the 1,147 patients randomized, a total of 1,073 patients received LEXISCAN and had interpretable SPECT scans at all visits; 538 in Group 1 and 535 in Group 2. The median age of the patients was 62 years (range 28 to 90 years) and included 633 (59%) men and 440 (41%) women.

Images from MPI 1 and MPI 2 for the two groups were compared for presence or absence of perfusion defects. The level of agreement between the MPI 1 and the MPI 2 reads in Group 1 was similar to the level of agreement between MPI 1 and MPI 2 reads in Group 2. However, two patients receiving LEXISCAN 3 minutes following inadequate exercise experienced a serious cardiac adverse reaction. No serious cardiac adverse reactions occurred in patients receiving LEXISCAN 1 hour following inadequate exercise stress [see ADVERSE REACTIONS, Pharmacodynamics].

Regadenoson is a stress agent that works by increasing blood flow in the arteries of the heart.

Regadenoson is given in preparation for a radiologic (x-ray) examination of blood flow through the heart to test for coronary artery disease.

Regadenoson may also be used for other purposes not listed in this medication guide.

You should not use this medication if you are allergic to regadenoson, or if you have a serious heart condition such as AV block or "sick sinus syndrome" (unless you have a pacemaker).

If you have any of these other conditions, you may need a dose adjustment or special tests:

• asthma or COPD (chronic obstructive pulmonary disease);
• a history of heart disease or high blood pressure; or
• if you have had a prolonged illness that caused vomiting or diarrhea.

FDA pregnancy category C. It is not known whether regadenoson is harmful to an unborn baby. Before you receive this medication, tell your doctor if you are pregnant.

It is not known whether regadenoson passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

Your doctor or pharmacist can provide more information about regadenoson.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

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The following adverse reactions are discussed in more detail in other sections of the labeling.

• Myocardial Ischemia [see WARNINGS AND PRECAUTIONS]
• Sinoatrial and Atrioventricular Nodal Block [see WARNINGS AND PRECAUTIONS]
• Atrial Fibrillation/Atrial Flutter [see WARNINGS AND PRECAUTIONS]
• Hypersensitivity, Including Anaphylaxis [see WARNINGS AND PRECAUTIONS]
• Hypotension [see WARNINGS AND PRECAUTIONS]
• Hypertension [see WARNINGS AND PRECAUTIONS]
• Bronchoconstriction [see WARNINGS AND PRECAUTIONS]
• Seizure [see WARNINGS AND PRECAUTIONS]
• Cerebrovascular Accident (Stroke) [see WARNINGS AND PRECAUTIONS]

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

During clinical development, 1,651 patients were exposed to LEXISCAN, with most receiving 0.4 mg as a rapid ( ≤ 10 seconds) intravenous injection. Most of these patients received LEXISCAN in two clinical studies that enrolled patients who had no history of bronchospastic lung disease as well as no history of a cardiac conduction block of greater than first-degree AV block, except for patients with functioning artificial pacemakers. In these studies (Studies 1 and 2), 2,015 patients underwent myocardial perfusion imaging after administration of LEXISCAN (N = 1,337) or ADENOSCAN (N = 678). The population was 26-93 years of age (median 66 years), 70% male and primarily Caucasian (76% Caucasian, 7% African American, 9% Hispanic, 5% Asian). Table 1 shows the most frequently reported adverse reactions.

Overall, any adverse reaction occurred at similar rates between the study groups (80% for the LEXISCAN group and 83% for the ADENOSCAN group). Aminophylline was used to treat the reactions in 3% of patients in the LEXISCAN group and 2% of patients in the ADENOSCAN group. Most adverse reactions began soon after dosing, and generally resolved within approximately 15 minutes, except for headache which resolved in most patients within 30 minutes.

Table 1 : Adverse Reactions in Studies 1 and 2 Pooled (Frequency ≥ 5%)

The frequency of rhythm or conduction abnormalities following LEXISCAN or ADENOSCAN is shown in Table 2 [see WARNINGS AND PRECAUTIONS].

Table 2 : Rhythm or Conduction Abnormalities* in Studies 1 and 2

In a randomized, placebo-controlled trial of 999 patients with asthma (n = 532) or stable chronic obstructive pulmonary disease (n = 467), the overall incidence of pre-specified respiratory adverse reactions was greater in the LEXISCAN group compared to the placebo group (p < 0.001). Most respiratory adverse reactions resolved without therapy; a few patients received aminophylline or a short-acting bronchodilator. No differences were observed between treatment arms in the reduction of > 15% from baseline at two-hours in FEV1 (Table 3).

Table 3 : Respiratory Adverse Effects*

In a randomized, placebo-controlled trial of 504 patients (LEXISCAN n=334 and placebo n=170) with a diagnosis or risk factors for coronary artery disease and NKFK/DOQI Stage III or IV renal impairment (defined as GFR 15-59 mL/min/1.73 m²), no serious adverse events were reported through the 24-hour follow-up period.

In an open-label, multi-center trial evaluating LEXISCAN administration following inadequate exercise stress, 1,147 patients were randomized into one of two groups. Each group underwent two LEXISCAN stress myocardial perfusion imaging (MPI) procedures. Group 1 received LEXISCAN 3 minutes following inadequate exercise in the first LEXISCAN stress (MPI 1). Group 2 rested 1 hour after inadequate exercise to allow hemodynamics to return to baseline prior to receiving LEXISCAN (MPI 1). Both groups returned for a second stress MPI 1-14 days later and received LEXISCAN without exercise (MPI 2).

The most common adverse reactions are similar in type and incidence to those in Table 1 above for both Groups. The timing of the administration of LEXISCAN did not alter the common adverse reaction profile.

Table 4 shows a comparison of cardiac events of interest for the two groups [see WARNINGS AND PRECAUTIONS]. The cardiac events were numerically higher in Group 1.

Table 4 : Cardiac Events of Interest in Inadequate Exercise Stress Study

Post-Marketing Experience

The following adverse reactions have been reported from worldwide marketing experience with regadenoson. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Myocardial infarction, cardiac arrest, ventricular arrhythmias, supraventricular tachyarrhythmias including atrial fibrillation with rapid ventricular response (new-onset or recurrent), atrial flutter, heart block (including third-degree block), asystole, marked hypertension, symptomatic hypotension in association with transient ischemic attack, acute coronary syndrome (ACS), seizures and syncope [see WARNINGS AND PRECAUTIONS] have been reported. Some events required intervention with fluids and/or aminophylline [see OVERDOSAGE]. QTc prolongation shortly after LEXISCAN administration has been reported.

Tremor, seizure, transient ischemic attack, and cerebrovascular accident including intracranial hemorrhage [see WARNINGS AND PRECAUTIONS].

Abdominal pain, occasionally severe, has been reported a few minutes after LEXISCAN administration, in association with nausea, vomiting, or myalgias; administration of aminophylline, an adenosine antagonist, appeared to lessen the pain. Diarrhea and fecal incontinence have also been reported following LEXISCAN administration.

Anaphylaxis, angioedema, cardiac or respiratory arrest, respiratory distress, decreased oxygen saturation, hypotension, throat tightness, urticaria, rashes have occurred and have required treatment including resuscitation [see WARNINGS AND PRECAUTIONS].

Musculoskeletal pain has occurred, typically 10-20 minutes after LEXISCAN administration; the pain was occasionally severe, localized in the arms and lower back and extended to the buttocks and lower legs bilaterally. Administration of aminophylline appeared to lessen the pain.

Respiratory arrest, dyspnea and wheezing have been reported following LEXISCAN administration.

Read the entire FDA prescribing information for Lexiscan (Regadenoson Injection)