NATPARA Flashcards
Normal PTH Levels
10-60 pg/mL (normal physiological range)
Normal calcium
8.4-10.6 mg/dL
What is the PDUFA date?
January 24
Positioning
NATPARA is the first and only PTH replacement therapy for hypoparathyroidism that directly treats the condition physiologically giving patients better health today while preventing complications tomorrow
Payer Mix
61% private, 35% public, 4% uninsured (from Vertical Health)
PTH Intestine
PTH stimulates conversion of 25 hydroxy to 1,25 dihydroxy which enhances the absorption of calcium
PTH Kidney
PTH stimulates renal reabsorption of calcium and promotes phosphate excretion.
PTH Bone
PTH stimulates bone resorption which delivers calcium and phosphate into the circulation.
Pharmacokinetics
Peak plasma concentrations Tmax occur within 5 to 30 minutes with a second smaller peak at 1 to 2 hours. Half life was 3.02 and 2.83 hours for the 50 and 100 mcg doses.
Absorption
Absolute bioavailability of 55%.
Distribution
Volume of distribution of 5.35L at steady state.
Metabolized
Clearance is primarily hepatic with a lesser role played by the kidneys.
Excretion
In the liver, most intact PTH is cleaved by cathepsins. In the kidney, most is filtered at the glomerulus.
Tetany
Involuntary contraction of muscle.
Paresthesias
Sensation of tingling, tickling, prickling, pricking, burning.
WW Forecast
$1.3B in 2023
Prevalence
53,000 with 24,500 uncontrolled and 17,500 with an Endo.
Addressable population
53,000 prevalence
24,380 uncontrolled
17,500 seeing an Endo
Specialty Pharmacy
Accredo Express Scripts, CVS Caremark, Walgreens (Diplomat is largest independent)
Number of Endos (SK&A)
5,266 in 2,830 accounts.
3,300 Endo Practices
1,966 Multi-Specialty
REPLACE Number of Patients
124 patients; 84 NATPARA; 40 Placebo
134 patients; 90 NATPARA; 44 Placebo
Hallmarks of the disease
Hypocalcemia, hyperphosphatemia (worsened by active vit D administration) hypercalciuria (worsened by calcium and vit D administration). The 3 H’s.
REPLACE Target Serum Calcium at Optimization
8.0 to 9.0 mg/dL with a minimum of 7.5.
REPLACE List of Secondary Endpoints
Percent change in oral calcium, active vitamin D independence, frequency of hypocalcemia symptoms between wk 16 and 24.
REPLACE Efficacy Serum Calcium Target
> 7.5 mg/dL or baseline and below ULN or 10.6
REPLACE Primary results
55% (46/84) met the primary endpoint vs 3% (1/40) on placebo (in label)
53% (48/90) met the primary endpoint vs 2% (1/44) on placebo.
REPLACE Percent Change in Oral Calcium at Week 24
52% SS reduction vs 7% increase in placebo (not in label)
52% SS reduction vs 6% increase in placebo.
REPLACE patients with symptoms of Hypocalcemia from week 16 to 24
The difference did not reach statistical significance 35% NATPARA vs 38% placebo (not in label)
REPLACE reduction in calcium/phosphate product
SS Mean change decrease from baseline of -5.5 NATPARA vs -0.5 Placebo (not in label)
Baseline NATPARA 39.8 and Placebo 40.8
Week 24 NATPARA 34.8 and Placebo 39.9
REPLACE List of Exploratory Endpoints
Changes in urinary calcium, calcium-phosphate product, bone effects, quality of life.
REPLACE Active Vitamin D Independence
42% (35/84) of patients achieved independence and took <500 mg/day of oral calcium vs 3% (1/40) placebo (on label)
REPLACE Serum Phosphate Results
Serum phosphate levels were significantly decreased from baseline from 4.53mg/dL to 4.03. Placebo was unchanged (off label)
Label: Immunogenicity
Incidence rate of anti-PTH antibodies was 8.6% (3/35) and 5.9% (1/17) in subjects who rec’d subcuateous administration of 50 to 100 mcg NATPARA or placebo once daily for 24 weeks (NEW LABEL)
Label: Immunogenicity across all studies
The immunogenicity incidence rate was 16.1% (14/87). These 14 subjects had low titer anti-bodies and of these, 3 subjects subsequently became antibody negative.
REPLACE How was the titration done?
A pre-specified algorithm vs a flexible one that was used in RACE.
REPLACE Treatment Phase
24 wk treatment with a 12 wk titration phase and 12 wk maintenance phase where Natpara could be reduced but not increased.
Label Adverse Reactions
Paraesthesia (31% vs 25%), hypocalcemia (27% vs 23%), headache (25% vs 23%), hypercalcemia (19% vs 3%), nausea (18% vs 18%).
Phase 1 Phosphate Excretion
24 hour urinary phosphate excretion was increased by 51% (50 mcg) and 60% (100 mcg).
REPLACE Duration
24 weeks treatment and 4 weeks follow up.
REPLACE Vitamin D Reduction at 24 weeks
78% reduction in the NATPARA group vs 30% placebo. Not in the label.
REPLACE Discontinuation
6 (6.6%) on Natpara 7 (15.9%) on placebo.
REPLACE Compliance
Compliance of 80% or higher in 98% of Natpara patients and 96% of placebo. (This meant that 98% of pts administered over 80% of the prescribed dose as measured by returned supplies)
REPLACE Dose Distribution
56% on 100 mcg, 26% on 75mcg, 18% on 50 mcg.
Edited post FDA
REPLACE Baseline Urinary Calcium
Mean urinary calcium exceeded 300 mg/24 hr in both groups. 361 mg/24 hr Natpara and 338 placebo.
Mean urinary calcium exceeded 300 mg/24 hr in both groups. 354 mg/24 hr Natpara and 345 placebo.
REPLACE Bone Data
Bone turnover markers were in the lower part of normal range and increased BMD at baseline confirmed the presence of adynamic bone disease. After 24 wks of treatment there was a marked increase in all bone turnover markers and a mean decrease in BMD in the hip which was not significant at the lumbar spine and the distal third of the radius. There was no increase in BTM markers and a slight increase in BMD in the placebo group.
REPLACE Bone Marker Results
Increased CTX a resorption marker and BSAP a formation marker.
RACE Study Design
12 month open label study extension study