Gene Therapy Player REGENXBIO's RGX-121 Marks Success In Trial, Yet Faces Challenges In A Crowded Market: Analyst

Last Wednesday,  REGENXBIO Inc RGNX reported additional interim safety and efficacy in the Phase 1/2 AFFINITY DUCHENNE trial of RGX-202 in patients with Duchenne muscular dystrophy ages 4 to11 years old.

In new data from the third patient, aged 6.6 years, who received RGX-202 at dose level 1, RGX-202 microdystrophin expression was measured to be 83.4% compared to control at three months. 

REGENXBIO also announced topline results from the Phase 1/2/3 CAMPSIITE trial of RGX-121 in patients up to 5 years old diagnosed with Mucopolysaccharidosis Type II (MPS II), also known as Hunter syndrome.

The trial met its primary endpoint with statistical significance.

Wedbush writes that the supplementary data from the Ph1/2 AFFINITY DUCHENNE trial provides additional confirmation of RGX-202’s clinical effectiveness. 

However, a more comprehensive evaluation awaits functional data later this year to determine if the inclusion of the CT terminal domain indeed results in greater functional benefits.

The analyst reiterates the Neutral rating, with a price target of $21.

In addition, the market potential for RGX-202 is constrained by Sarepta Therapeutics Inc’s SRPT Elevidys and its possible label expansion. 

The entry of Pfizer Inc’s PFE fordadistrogene movaparvovec before RGX-202 further limits its market opportunity. 

Wedbush current sales projection for RGX-202/DMD in fiscal year 2030 is $93.8 million, assuming a U.S. launch in February 2027.

For RGX-121/MPS II, the positive outcomes in CSF D2S6 reduction and a favorable safety profile during the pivotal phase of the Ph1/2/3 CAMPSIITE trial suggest potential FDA approval. 

The analyst notes that the MPS II market is relatively small, with an estimated 441 patients in the U.S. 

Additionally, the emergence of blood-brain barrier (BBB)-crossing enzyme replacement therapies (ERTs) like Denali Therapeutics Inc’s DNLI tividenofusp alfa and JCR Pharmaceuticals Co Ltd’s pabinafusp alfa could pose a challenge to RGX-121, especially given that around 67% of MPS II patients have the neuronotropic form and may be eligible for these late-stage BBB-crossing ERTs.

Price Action: RGNX shares are up 9.50% at $17.75 on the last check Monday.