Genentech has received FDA approval for Enspryng (satralizumab-mwge), a subcutaneous (SC) treatment for thyroid eye disease (TED).
The announcement follows just three months after the federal agency granted priority review.
Wait, I thought Enspryng was already approved … ?
It was: for neuromyelitis optic spectrum disorder (NMOSD) in 2020.
Details on that—plus the other two indications it’s currently under clinical investigation for—can be found here.
And while this marks the second indication for the therapy, it also makes it the first at-home treatment option for TED patients.
Gotcha. Now let’s get a rundown on it.
Developed by Chugai (another member of the Roche Group), the prescription-based therapy (pronounced EN-SPRING) is formulated as a humanized monoclonal antibody (mAb).
What it does: targets the receptor activity of interleukin-6 (IL-6), which plays a critical role as a chemical messenger involved in the body’s inflammatory response.
The basis for its design: is a novel recycling antibody technology that enables sustained IL-6 inhibition by “binding strongly and repeatedly to the IL-6 receptor,” which in turn allows for rapid and sustained suppression of inflammatory pathways.
And its official indication?
Enspryng’s prescribing information (PI) has updated its indications and usage section to include for the treatment of TED regardless of TED activity or duration in adult patients.
And the dosage + administration?
Administered as a single-dose prefilled autoinjector, the exact dosage is determined by a patient’s body weight. As per the PI:
For a body weight of 40-100 kg (88.18 to 220.45 lbs):
- First three administrations: 120 mg via SC injection at Weeks 0, 2, and 4.
- Following this, a maintenance dosage of 120 mg every 4 weeks (Q4W).
For a body weight >100 kg (220.45 lbs):
- First three administrations: 180 mg via SC injection at Weeks 0, 2, and 4.
- Following this, a maintenance dosage of 180 mg Q4W.
Does a physician need to administer this?
Nope. The SC injection can be administered by the patient themselves or a caregiver (following training from a healthcare provider, that is).
Noted. So what clinical data supported this approval?
That would be the phase 3 SatraGO program, which comprised two global, randomized, placebo-controlled studies:
- SatraGO-1 (NCT05987423)
- SatraGO-2 (NCT06106828)
What to know: As Genentech reported last year, the “totality of data” from the program showed that Enspryng delivered:
- consistent, clinically meaningful improvements across key TED signs and symptoms
- a favorable safety profile that set it apart from currently available TED treatments
Did both studies meet their primary goals?
Nope—the two trials diverged on the primary outcome:
- SatraGO-1: 49% of Enspryng-treated patients achieved a proptosis response, compared with 39% on placebo
- The difference was not statistically significant
- SatraGO-2: 53% of Enspryng-treated patients achieved a proptosis response, compared with 23% on placebo
- The difference was statistically significant
Despite SatraGo-1’s short falls, Genentech said the numerical improvement offered “additional confirmatory evidence regarding the potential benefit of satralizumab in this setting.”
What about secondary endpoints?
Those were more promising, as both studies showed improvements on secondary measures. In patients with active TED:
- SatraGO-1: 78% had a reduction in clinical activity score (CAS), and 44% had improved diplopia
- SatraGO-2: 90% had a reduction in CAS, and 61% had improved diplopia
Gotcha. Now let’s talk adverse reactions.
Enspryng’s safety profile in the SatraGO trials was reported to be consistent with its known profile for NMOSD.
- In those studies, the most common adverse events (AEs) among Enspryng-treated patients included nasopharyngitis, headache, influenza, abdominal pain, back pain, diarrhea, and nausea.
And per its PI, the most common AEs observed among TED patients (occurring in at least 5%) included upper respiratory tract infection and an increase in alanine aminotransferase (ALT).
Check out a few others here.
Any contraindications or other precautions to keep in mind?
Contraindications: known hypersensitivity to satralizumab or any of Enspryng’s inactive ingredients; active hepatitis B infection, as well as active or untreated latent tuberculosis.
As for warnings and precautions: Prescribing physicians should be aware of:
- Administration should be delayed if a patient presents with an active infection until it’s resolved.
- ALT and aspartate aminotransferase (AST) levels should be monitored during treatment; an interruption of dosing may be needed.
- Decreased neutrophil counts may occur and, as such, should be monitored during treatment.
See here for more potentially serious side effects.
Duly noted. So what do we know about commercial availability?
While Enspryng is already commercially available in the United States for its NMOSD indication, Genentech did not explicitly provide an update or any specific timeframe for when this TED indication will be on the market.
Click here to reach out to a Genentech representative for more information.