Stage B2 Preclinical MMVD: Effectiveness of VETMEDIN for the delay of onset of CHF in dogs diagnosed with Stage B2 preclinical MMVD is based on results from two multi-site field studies.
Study 1: The first study was a multicenter, vehicle-controlled field study. This study demonstrated a significant delay in the onset of CHF in dogs with cardiomegaly and heart murmur secondary to Stage B2 MMVD when treated with VETMEDIN at the targeted total daily dose of 0.23 mg/lb (0.5 mg/kg) divided into two administrations approximately 12 hours apart.
A total of 363 dogs across various breeds were randomized to treatment. The resulting population evaluated for effectiveness consisted of 343 dogs receiving either VETMEDIN (n=173) or vehicle control chewable tablets (n=170).
Dogs ranged between 6 and 17 years of age and weighed between 9 and 33 lbs (4.1 to 15.1 kg) at enrollment. Dogs were confirmed to have evidence of Stage B2 preclinical MMVD prior to enrollment, including a systolic heart murmur grade of ≥3/6 and radiographic and echocardiographic evidence of cardiomegaly, including a VHS >10.5, LA/Ao ratio ≥1.6, and LVIDDN ≥1.7.
Dogs were ineligible if they were found to have current or previous evidence of cardiogenic pulmonary edema, clinically significant tachyarrhythmias, cardiac disease other than MMVD, significant systemic disease, evidence of pulmonary hypertension (RA:RV gradient >65 mmHg), or were pregnant or lactating.
The primary endpoint evaluated was a composite of the development of left-sided CHF, cardiac-related death or euthanasia. Left-sided CHF was confirmed by radiographic evidence of cardiogenic pulmonary edema. If a dog died in the absence of evidence of a non-cardiac cause of death, prior to radiographic confirmation of pulmonary edema, it was also considered to have reached the primary endpoint. The study was designed to follow individual dogs for up to 3 years or until disease progressed to a primary endpoint.
At study termination, 42.2% of the dogs in the VETMEDIN group had reached the primary endpoint, compared to 53.5% in the vehicle control group. The median time to the primary endpoint was 1127 days in the VETMEDIN group compared to 732 days in the vehicle control group. Thus, administration of VETMEDIN to dogs with Stage B2 preclinical MMVD resulted in the prolongation of the primary endpoints by 395 days (13.2 months) compared to dogs receiving vehicle control product. The time to onset of verified CHF was evaluated as a separated component of the primary endpoint. The median time to onset of CHF was 1231 days in the VETMEDIN group versus 806 days in the control group. Thus, administration of VETMEDIN to dogs with Stage B2 preclinical MMVD resulted in the prolongation of the time to onset of verified CHF by 425 days (14.2 months), compared to dogs receiving vehicle control product.
Study 2: The second study was a historically controlled, multi-site field study. As in the first study, dogs were treated with VETMEDIN at the targeted total daily dose of 0.23 mg/lb (0.5 mg/kg) divided into two administrations approximately 12 hours apart. While Study 1 enrolled all dogs with Stage B2 MMVD (LA/Ao ratio ≥1.6), Study 2 enrolled a subset of dogs with Stage B2 MMVD and more advanced cardiomegaly (LA/Ao ratio ≥1.8). The historical control for Study 2 was derived from the vehicle control group from Study 1 (described above) and included dogs with an LA/Ao ratio ≥1.8.
A total of 161 dogs across various breeds were treated with at least one dose of VETMEDIN. The number of dogs included in the population for effectiveness was 125 dogs. Dogs ranged between 6 and 16 years of age and weighed between 9 and 33 lbs (4.1 to 15.0 kg) at enrollment. Dogs were confirmed to have evidence of Stage B2 preclinical MMVD prior to enrollment, including a systolic heart murmur grade of ≥3/6 and evidence of cardiomegaly, including a VHS >10.5, and echocardiographic evidence of LA/Ao ratio ≥1.8.
Dogs were ineligible if they were found to have current or previous evidence of cardiogenic pulmonary edema, clinically significant tachyarrhythmias, current or previous evidence of coughing that interferes with the clinical assessment of progressing clinical signs, current or previous evidence of syncope, cardiac disease other than MMVD, significant systemic disease, evidence of clinically relevant pulmonary hypertension (RA:RV gradient >65 mmHg), or were pregnant or lactating.
The primary endpoint was individual treatment success or failure for each animal. A dog was considered a treatment success if it had no radiographic evidence of CHF at or before Day 365 AND did not develop malignant arrhythmias, syncope, significant coughing, and/or increased resting respiratory rate, requiring concomitant therapy at or before Day 365. A dog was considered a treatment failure if at or before Day 365 it developed clinical signs of CHF with radiographic evidence documented and confirmed by an independent verification committee; or it was euthanized or died in the absence of evidence of a non-cardiac cause of death; or it developed malignant arrhythmias, syncope, significantly increased RRR and/or advanced coughing that required concomitant therapy in absence of radiographic CHF.
Left-sided CHF was confirmed by radiographic evidence of cardiogenic pulmonary edema with left-sided cardiomegaly. In addition to the radiographic confirmation of CHF, dogs had to exhibit contemporaneous clinical signs consistent with left-sided CHF, such as increased respiratory rate and effort, cough, orthopnea, and elevated heart rate without sinus arrhythmia. The study was designed to follow individual dogs for up to 365 days or until disease progressed to a primary endpoint.
By Day 365, 79.2% of dogs on study were treatment successes, with a 2-sided 95% confidence interval (0.7026, 0.8594), which met the study success criteria of the lower bound of the 95% confidence interval greater than or equal to 54% and the estimated success rate for the IVP greater than or equal to 65%.
Clinical MMVD or DCM: Effectiveness of VETMEDIN for the management of the signs of mild, moderate, or severe CHF in dogs due to clinical MMVD or DCM is based on a separate study – a double-masked, multi-site, 56-day field study, in which 355 dogs with modified New York Heart Association‡ (NYHA) Class II, III, or IV CHF due to MMVD or DCM were randomly assigned to either the active control (enalapril maleate) or the VETMEDIN (pimobendan) treatment group. Of the 355 dogs, 52% were male and 48% were female; 72% were diagnosed with MMVD and 28% were diagnosed with DCM; 34% had Class II, 47% had Class III, and 19% had Class IV CHF. Dogs ranged in age and weight from 1 to 17 years and 3.3 to 191 lbs, respectively.
The most common breeds were mixed breed, Doberman Pinscher, Cocker Spaniel, Miniature/Toy Poodle, Maltese, Chihuahua, Miniature Schnauzer, Dachshund, and Cavalier King Charles Spaniel. The 180 dogs (130 MMVD, 50 DCM) in the active control group received enalapril maleate (0.5 mg/kg once or twice daily), and all but 2 received furosemide. Per protocol, all dogs with DCM in the active control group received digoxin. The 175 dogs (126 MMVD, 49 DCM) in the VETMEDIN group received pimobendan (0.5 mg/kg/day divided into 2 portions that were not necessarily equal, and the portions were administered approximately 12 hours apart), and all but 4 received furosemide. Digoxin was optional for treating supraventricular tachyarrhythmia in either treatment group, as was the addition of a β-adrenergic blocker if digoxin was ineffective in controlling heart rate. After initial treatment at the clinic on Day 1, dog owners were to administer the assigned product and concurrent medications for up to 56±4 days.
The determination of effectiveness (treatment success) for each case was based on improvement in at least 2 of the 3 following primary variables: modified NYHA classification, pulmonary edema score by a masked veterinary radiologist, and the investigator’s overall clinical effectiveness score (based on physical examination, radiography, electrocardiography, and clinical pathology). Attitude, pleural effusion, coughing, activity level, furosemide dosage change, cardiac size, body weight, survival, and owner observations were secondary evaluations contributing information supportive to product effectiveness and safety.
Based on protocol compliance and individual case integrity, 265 cases (134 VETMEDIN, 131 active control) were evaluated for treatment success on Day 29. See Table 7 for effectiveness results.
Table 7: Effectiveness Results for the 56-Day Field Study
| - VETMEDIN
- Group
| - Active Control Group
|
- Treatment Success on Day 29
| - 80.7%
- n = 134
| - 76.3%
- n = 131
|
- 88 of 101 dogs
- with MMVD
| - 77 of 100 dogs
- with MMVD
|
- 20 of 33 dogs
- with DCM
| - 23 of 31 dogs
- with DCM
|
- Treatment Success on Day 56
| - 71.1%
- n = 113
| - 67.2%
- n = 110
|
- 66 of 85 dogs
- with MMVD
| - 56 of 85 dogs with MMVD
|
- 13 of 28 dogs
- with DCM
| - 17 of 25 dogs
- with DCM
|
- No increase in furosemide dose between Day 1 and Day 29
| - 78.3%
- n = 130
| - 68.6%
- n = 126
|
At the end of the 56-day study, dogs in the VETMEDIN group were enrolled in an unmasked field study to monitor safety under extended use, without restrictions on concurrent medications.
VETMEDIN was used safely in dogs concurrently receiving furosemide, digoxin, enalapril, atenolol, spironolactone, nitroglycerin, hydralazine, diltiazem, antiparasitic products (including heartworm disease prevention), antibiotics (metronidazole, cephalexin, amoxicillin-clavulanate, fluoroquinolones), topical ophthalmic and otic products, famotidine, theophylline, levothyroxine sodium, diphenhydramine, hydrocodone, metoclopramide, and butorphanol, and in dogs on sodium-restricted diets.
‡The modified NYHA classification was historically used to stage dogs with heart disease.
A dog with modified NYHA Class II heart failure has fatigue, shortness of breath, coughing, etc. apparent when ordinary exercise is exceeded.
A dog with modified NYHA Class III heart failure is comfortable at rest, but exercise capacity is minimal.
A dog with modified NYHA Class IV heart failure has no capacity for exercise and disabling clinical signs are present even at rest.