Strensiq
Strensiq (asfotase alfa) is the only medication approved for use in people with a rare, genetic condition called hypophosphatasia. This medication is given as an injection under the skin 3 to 6 times per week. It's only available as a brand medication, which can be expensive.
What is Strensiq (asfotase alfa)?
What is Strensiq (asfotase alfa) used for?
- Perinatal-onset hypophosphatasia (HPP), occurring before or shortly after birth
- Infantile-onset HPP, occurring between birth and 6 months of age
- Juvenile-onset HPP, occurring in childhood or up to 18 years of age
How Strensiq (asfotase alfa) works
Strensiq (asfotase alfa) is an enzyme replacement therapy. In hypophosphatasia, your body isn't able to make an enzyme (protein) called alkaline phosphatase (ALP). This enzyme is important for bone health. Without enough ALP, normal bone mineralization, or the building of strong bones, can't happen.
Strensiq (asfotase alfa) serves as a replacement for ALP, which allows your body to build healthy and strong bones.
Drug facts
Side effects of Strensiq (asfotase alfa)
The following side effects may get better over time as your body gets used to the medication. Let your healthcare provider know immediately if you continue to experience these symptoms or if they worsen over time.
Common Side Effects
- Redness at injection site (41-75%)
- Abnormal distribution of fat around the injection site (lipodystrophy, 18-70%)
- Buildup of calcium phosphate crystals in the body (ectopic calcification, 4-55%)
- Discoloration at injection site (15-40%)
- Pain at injection site (14-40%)
- Itching at injection site (13-35%)
- Swelling at injection site (10-30%)
- Bruising at injection site (8-20%)
Less Common Side Effects
- Vomiting
- Kidney stones
- Low blood calcium levels
- Low vitamin B6 levels
Strensiq (asfotase alfa) serious side effects
Contact your healthcare provider immediately if you experience any of the following.
- Allergic reactions: hives, rash, blisters, skin reddening, swelling of the lips or tongue, difficulty breathing
The following Strensiq (asfotase alfa) side effects have also been reported
Side effects that you should report to your care team as soon as possible:
- Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
- Kidney stones—blood in the urine, pain or trouble passing urine, pain in the lower back or sides
- Vision loss
Side effects that usually do not require medical attention (report these to your care team if they continue or are bothersome):
- Change in skin color at injection site
- Lipodystrophy—hardening or scarring of tissue at injection site
- Pain, redness, or irritation at injection site
Pros and cons of Strensiq (asfotase alfa)
Pros
- Works well to treat HPP
- Given 3 to 6 times per week
- Has been studied in children and adults
Cons
- Needs to be injected under the skin
- Might be difficult for some people to administer correctly
- Brand name only, which can be expensive
Pharmacist tips for Strensiq (asfotase alfa)
- Before starting this medication, make sure your or your child's provider or pharmacist teaches you how to give Strensiq (asfotase alfa). Learning to use Strensiq (asfotase alfa) correctly will help avoid accidental injuries or medication waste. Carefully read the instructions on how to give the injection. Contact your or your child's provider or pharmacist if you have any questions on how to use this medication.
- Store Strensiq (asfotase alfa) in the refrigerator and keep the vials in the original carton away from light. When it's time to give the dose, take the medication out of the refrigerator and allow it to reach room temperature. This will take about 15 to 30 minutes. Don't try to warm up the medication any other way (e.g., microwave, under hot water) because you might damage it. Once out of the refrigerator, use the medication within 3 hours.
- Always check to make sure the medication is clear or milky white, colorless to slightly yellow before using it. It's okay if there are a few small white particles (solid pieces) present. If it's cloudy, discolored, or has many particles, don't use it. Contact your or your child's provider or pharmacist to see if it's possible to get a replacement.
- Each Strensiq (asfotase alfa) vial provides a single dose of medication. You must throw away any leftover medication after each use, even if there's still some remaining in the vial. This is because the vial doesn't contain any preservatives to keep germs and bacteria out of the medication once you open it.
- After giving yourself the medication, throw away the syringe and needle in a sharps container or something made of heavy-duty plastic (e.g., empty milk carton, laundry detergent bottle) to lower the risk of needle-stick injuries. Don't throw them away in your trash can. When your sharps container is almost full, close it tightly with the cap. For more information on how to throw away your sharps container safely and guidance for your specific state, visit the FDA's website.
Common questions about Strensiq (asfotase alfa)
Hypophosphatasia (HPP) is a rare, genetic problem that causes weak bones and teeth. This happens because the body can't make an enzyme called alkaline phosphatase correctly. This enzyme is important for bone mineralization. If it doesn't work properly, the body can't build strong bones. Signs and symptoms of HPP differ by age, but generally include poorly developed parts of the body, inability to grow, weak bones that cause pain, and difficulty performing everyday activities. Strensiq (asfotase alfa) helps, because it replaces the missing enzyme responsible for bone mineralization. This helps build strong bones.
You can give the injection under the skin in the stomach, upper arms, upper legs, or buttocks. Never inject in the buttock area for babies. Also, never inject the medication into a muscle or vein. To lower the risk of bruising and irritation, rotate between different injection sites each time so that the same area isn't used repeatedly. Don't inject into skin that's red, hot, or swollen to avoid further damaging the skin.
Since HPP is a genetic problem, you'll need to take Strensiq (asfotase alfa) for your entire life. Continue taking the medication as long as it's helping your condition and you're not having severe side effects.
It's possible to travel with Strensiq (asfotase alfa), but it requires careful planning and coordination. Since this medication needs to be refrigerated (but not frozen) at all times, it's important to plan ahead and make arrangements to make sure this is possible and that the medication is carefully handled. Pack enough injection supplies and check with your travel destination about refrigeration. When traveling, keep Strensiq (asfotase alfa) in an insulated cooler with ice or an ice pack. For plane trips, contact the airline to see if refrigeration or additional ice is available during the flight. There is a travel letter available to help explain the medication's storage and handling requirements to airline staff.
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Risks and warnings for Strensiq (asfotase alfa)
Strensiq (asfotase alfa) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Severe allergic reactions
Severe allergic reactions to Strensiq (asfotase alfa) are possible, including life-threatening reactions like facial swelling, shock, and anaphylaxis (closing of the throat). If you notice dizziness, a choking sensation, nausea, swelling around your eyes, swelling of the lips or tongue, or difficulty breathing after using Strensiq (asfotase alfa), get medical attention right away.
Abnormal distribution of fat (lipodystrophy) around the injection site
Strensiq (asfotase alfa) can cause lipodystrophy around the injection site. People have reported this happening after using the medication for several months. To lower your risk for lipodystrophy, make sure you rotate injection sites so you're not injecting into the same location over and over again. Also, make sure you're injecting the medication using good technique. If you're not sure how to use Strensiq (asfotase alfa), contact your or your child's pharmacist or provider.
Ectopic calcifications
In general, people with HPP are at higher risk for developing ectopic calcifications, which is a buildup of calcium phosphate crystals in the body. This can happen in the eyes or kidneys. It's not exactly known if the ectopic calcifications reported by people taking Strensiq (asfotase alfa) were from the medication or HPP. It's recommended that your or your child's eyes and kidneys are monitored before and during treatment with Strensiq (asfotase alfa). If you or your child has any changes in vision or has difficulty urinating while taking this medication, contact your or your child's provider. Testing might be available to see if there are calcium phosphate crystals forming in the body.
Lower response to Strensiq (asfotase alfa) due to antibody formation
Most people taking Strensiq (asfotase alfa) in clinical studies developed antibodies to Strensiq (asfotase alfa). These antibodies can interfere with how well the medication works. If any HPP symptoms get better but then worsen while taking Strensiq (asfotase alfa), contact your or your child's provider because there might be special antibody testing available.
Strensiq (asfotase alfa) dosage
Typical dosage for Strensiq (asfotase alfa)
The dose is based on body weight. Your or your child's provider will determine the right dose.
- Perinatal- and infantile-onset HPP: The typical dose is 2 mg/kg of body weight injected under the skin three times per week, or 1 mg/kg of body weight six times per week. Your child's provider might raise the dose to 3 mg/kg of body weight three times per week depending on how your child responds to the medication.
- Juvenile-onset HPP: The typical dose is 2 mg/kg of body weight injected under the skin three times per week, or 1 mg/kg of body weight six times per week.