Regenxbio (NASDAQ: RGNX) shares nosedived 43% over two days late last week, reaching 52-week lows on consecutive days, despite generating positive pivotal Phase III data for its Duchenne muscular dystrophy (DMD) gene therapy candidate RGX-202.
While the data was encouraging enough to enable discussion of Regenxbio bringing a second DMD gene therapy to the market, investors and analysts concluded it was not encouraging enough to pose a competitive threat to the developer of the first marketed DMD gene therapy, Sarepta Therapeutics (NASDAQ: SRPT), or to Solid Biosciences (NASDAQ), whose DMD gene therapy candidate SGT-003 is in Phase III as well as Phase I/II trials.
Even worse, investors were jolted by Regenxbio’s disclosure that the FDA had recommended the company conduct a randomized controlled trial (RCT) to assess RGX-202 in DMD during talks with agency officials. Regenxbio sought to reassure investors in its first-quarter earnings press release by noting past FDA guidance that externally controlled trials “may be adequate for demonstrating substantial evidence of effectiveness, especially when the treatment effect is sufficiently large enough to overcome limitations of externally controlled trials.”
Regenxbio plans to discuss its data with FDA officials at a future meeting. The agency has offered to review the RGX-202 data and alternative proposals, according to the company.
“RGX-202 pivotal data point to potential entry of second DMD gene theory, but a possibility of RCT requirement makes market entry timing unclear,” Kostas Biliouris, PhD, a managing director on the biotechnology research team of Oppenheimer & Co., wrote in a research note.
If the FDA does not insist on an RCT, RGX-202 could gain accelerated approval in 2027, Biliouris noted. Otherwise, the gene therapy is looking at not reaching the market for at least three additional years.
“Completing an RCT study as a precursor to filing or a precursor to approval means that it’s very unlikely that any new gene therapy would be approved until 2030. And I think that scenario is really untenable for the [DMD] community,” Simpson said. “It’s the opposite of regulatory flexibility.”
These regulatory and competitive concerns sent investors scrambling to sell Regenxbio shares late last week. The shares tumbled 38% from $10.04 to $6.24 Thursday, then slid another 8% Friday, sinking to $5.72 at the closing bell.
Positive microdystrophin expression
Regenxbio’s stock woes came despite the company announcing positive results from its pivotal Phase III portion of the Phase I/II/III AFFINITY DUCHENNE® trial (NCT05693142) of RGX-202. The company said the trial met its primary endpoint as 93% of participants (28 of 30) reached at least 10% microdystrophin expression at Week 12. A 31st participant refused a muscle biopsy and, as a result, did not have a Week 12 biopsy available for evaluation.
Microdystrophin expression averaged 71.1% across all participants, and 41.6% in older boys, aged >8 years, with 80% of participants achieving >40% microdystrophin expression, Regenxbio said.
“High unmet need remains for Duchenne patients as current options face limitations related to efficacy, safety, and access. The untreated Duchenne population continues to grow in the United States and globally. Physicians and patients need new next-generation options,” Curran M. Simpson, president and CEO, told analysts on the company’s first quarter earnings call.
Regenxbio acknowledged two reports of treatment-related serious adverse events (~6.5% of treated patients): An 8-year-old patient developed subacute myocarditis, while a 10-year-old patient showed a case of asymptomatic liver injury.
“Both were easily managed and resolved within weeks without sequelae,” Simpson told analysts.
Biliouris acknowledged RGX-202’s positive microdystrophin but said it will not likely have a material impact on Sarepta and its marketed DMD gene therapy Elevidys® (delandistrogene moxeparvovec-rokl).
Limited likelihood
“RGX-202’s functional benefit remains unclear without RCT data, limiting the likelihood of AA [accelerated approval] given an already fully approved DMD gene therapy,” Biliouris said.
He added that RGX-202’s safety profile could deteriorate once the gene therapy reaches the market and is being administered to patients, as happened with Elevidys after some 800 had been treated with the therapy, prompting Sarepta to halt shipments of Elevidys for non-ambulatory patients and pause a Phase III trial.
The halt—plus a label update limiting Elevidys use to ambulatory patients—explains why the gene therapy’s net product revenue plunged 73% year-over-year in Q1, to $102 million from $375 million. Elevidys generated $898.7 million in 2025 revenue—it ranks second on GEN’s just published A-List of Top 10 Best-Selling Gene Therapies—which was 9.5% above 2024’s $820.8 million.
The Q1 sales decline has sent Sarepta’s stock into decline: From $23.06 on May 6, before releasing Q1 results after that day’s closing bell, Sarepta shares have slumped 22.5%, to $17.88 on Friday.
Elevidys sparked a showdown with the FDA last summer when the agency briefly demanded Sarepta also pause Elevidys shipments to ambulant patients following the second patient death tied to Elevidys, then reversed itself after, according to news reports, pleas to Congress, the FDA, and President Donald Trump by conservative leaders and DMD patient advocates—who launched a Change.org petition that garnered 1,900 signatures.
Competitive advantage
Despite the slumping sales and resulting stock decline, Biliouris noted that Sarepta and Elevidys have a significant competitive advantage over challengers: A 3-1/2 year first to market advantage, with statistically significant functional benefits reported from randomized trials, as well as what the analyst called “compelling” three-year positive topline follow-up data from ambulatory DMD patients in the 52-patient active arm in Part 1 of Sarepta’s EMBARK trial (Study SRP-9001-301, NCT05096221).
That data showed significant improvements in North Star Ambulatory Assessment (NSAA), Time to Rise (TTR), and 10-meter walk/run (10MWR).
“Even if RGNX secures AA, we expect minimal impact given the large DMD market size (can accommodate multiple companies) and potential Elevidys monopoly in the non-ambulatory market,” projected for 2027 and later, Biliouris wrote.
According to Sarepta, Duchenne affects approximately 1 in 3,500 to 5,000 males born worldwide—some 300,000 people worldwide, according to research and patient care group Cure Duchenne. In the United States, about 15,000 young men and a few young women live with DMD, according to Parent Project Muscular Dystrophy estimates. A 2019 study found that most people with DMD become non-ambulatory around ages 10–12 and need assisted ventilation at around 20 years of age.
Andrew Tsai, equity analyst with Jefferies, said Sarepta’s three-year data, including muscle MRI data, has only begun to be promoted by the company this year. Since it can take six months to go from “start form” initiating the treatment process to infusion with Elevidys, Tsai reasoned, “we expect momentum to rebuild progressively/steadily in Q3/Q4, restoring confidence in the ambulatory DMD oppty.”
Some ~80% of ambulatory DMD patients remain untreated, Tsai noted, while Sarepta told investors in its Q1 earnings presentation that more than 1,300 patients have been treated with Elevidys in commercial settings or clinical trials as of May 5.
“While Elevidys’ safety perception has changed, we think marketing efforts on muscle MRI data, long-term three-year EMBARK data, and no deaths in ambulatory DMD could entice patients/caregivers and physicians to adopt Elevidys more, widening the moat,” Tsai wrote.
Maury Raycroft, PhD, a colleague of Tsai and equity analyst with Jefferies, wrote that Regenxbio’s data “reinforces microdystrophin as a surrogate, which is constructive for SLDB [Solid Biosciences].”
Playing to strengths
However, Raycroft added that Regenxbio’s safety events (notwithstanding immunosuppression) and limited regulatory clarity absent a pivotal RCT “play into SLDB’s strengths,” such as its use of a steroid-only prophylactic immunomodulation regimen (no safety issues to date) and its ongoing Phase III IMPACT DUCHENNE trial (NCT07160634), which is an RCT, thus a derisking factor from a regulatory standpoint.
“We believe RGNX is relying on and will require reg[ulatory] flexibility, which incorporates add’l risk and limitations, especially w/ FDA leadership in flux,” Raycroft wrote. “We caught up w/ SLDB, who also pointed out that RGNX could run into challenges to run an RCT given their immunosuppressive regimen.”
That regimen consisted of sirolimus, eculizumab, and steroids that included prednisone, researchers from Regenxbio and clinical partners reported in a poster presented at the International Congress of the World Muscle Society, held October 7–11, 2025, in Vienna.
On May 7, Solid announced it had dosed the first patient in the IMPACT DUCHENNE trial in Australia, at the Children’s Hospital at Westmead. The multi-country, placebo-controlled, randomized, double-blind trial has a pre-specified primary endpoint of change from baseline at 18 months in time to rise from supine (TTR) velocity, based on a Type C meeting with the FDA.
“With the initiation of a randomized, placebo-controlled clinical trial, we are reinforcing our conviction in SGT-003 and our long-standing commitment to generating well-controlled, high-quality data,” Gabriel Brooks, MD, Solid’s chief medical officer, said in a statement.
Solid shares dipped 2% on news of the dosing, from $7.20 to $7.07. Since then, the shares have yo-oed, climbing 9% to $7.72 on May 12 but sliding 10% since then, to $6.92 on Friday.
In its Phase I/II INSPIRE DUCHENNE study (NCT06138639), SGT-003 has also been administered to 46 patients, with approximately 30 participants dosed as of year-end 2025, Solid said.
“Families living with Duchenne continue to face difficult treatment decisions in a setting of significant unmet medical need,” Brooks added. “Solid remains focused on helping inform the Duchenne community of potential additional treatment options through the responsible and rigorous clinical evaluation of SGT-003.”
uniQure, Replimune gain as Makary exits FDA
Two gene therapy developers saw their stocks enjoy significant gains after Martin A. Makary, MD, resigned as FDA commissioner.
Makary’s resignation on May 12 capped nearly a week of speculation that he was about to exit the agency after a turbulent 13-month tenure. That tenure was marked in part by the elimination of 3,500 FDA positions as part of the Elon Musk-led Department of Government Efficiency (DOGE)-directed federal job cuts—as well as more frequent rejections of biologics license applications (BLAs) for new therapies, particularly gene therapies in rare disease indications.
Those rejections were carried out by the agency’s Center for Biologics Evaluation and Research (CBER) during the two tenures of Vinayak (Vinay) Prasad, MD, as Center director. Prasad resigned the first time in August 2025 after less than three months at the CBER helm, after he led the FDA’s confrontation with Sarepta over patient deaths tied to Elevidys (see Regenxbio item, above). The second resignation was announced in March and took effect on April 30, after he led the FDA’s hardline stance and public criticism against uniQure (NASDAQ: QURE)’s Huntington’s disease (HD) gene therapy candidate AMT-130.
While uniQure stock roller-coastered after Prasad’s second resignation, the stock jumped 21% in the four trading days between May 8, when an unnamed-source report about Makary being fired first surfaced in The Wall Street Journal, and May 13, the day after he resigned. uniQure rose 14.5% from $24.15 to $27.66 the day of the WSJ report, plateaued on May 10, dipping two cents to $27.64, then resumed their climb, rising 5% to $29.10 the following day before inching up another 0.2% to $29.17 on Wednesday.
An even bigger winner among stocks, however, was Replimune Group (NASDAQ: REPL). The developer of oncolytic immunotherapies saw its shares rocket 59% after news surfaced of Makary exiting the FDA.
Replimune has found itself in the FDA’s crosshairs over its biologics license application (BLA) for its lead product candidate RP1 (vusolimogene oderparepvec) in combination with nivolumab to treat advanced melanoma, instead issuing two complete response letters (CRLs)—one in April 2025, the other last month.
On April 10, the FDA rejected Replimune’s BLA for a second time, issuing a complete response letter (CRL) contending that the data set upon which the agency’s breakthrough therapy designation was awarded was not sufficient to allow for RP1 approval—an assertion Replimune vehemently rejects.
Replimune responded to the second BLA by criticizing the FDA for an inconsistent review process, saying the agency contradicted earlier guidance to the company and assessed the resubmitted BLA through a different review team that replaced the team that previously interacted with the company.
Replimune also defended the combination therapy’s data in the Phase II IGNYTE trial (NCT03767348)—a 34% response rate with a median duration of 24.8 months and a favorable safety profile, the basis of the combo’s breakthrough therapy designation.
Following the first news report of a Makary firing in the works, Replimune shares jumped 22% from $3.34 to $4.07. After slipping 8% to $3.74 the following trading day (May 11), Replimune rose 9% to $4.09 the following day after Makary resigned—then vaulted 30% to $5.30 on Wednesday.
“Broadly, we see multiple options for experienced leaders who could help stabilize the Agency following the many leadership transitions, and believe the tendency toward the administration’s “Right to Try” could draw a next leader who is more permissive on drug approvals near-term positive on the space,” Brian Abrahams, MD, head of global healthcare research with RBC Capital Markets, wrote in a research note.
Abrahams put forward six possible permanent successors to Makary:
- Kyle Diamantas, current interim FDA commissioner; previously FDA deputy commissioner for human foods and senior counselor to Health and Human Services Secretary Robert F. Kennedy Jr.
- Stephen Hahn, MD, CEO of Nucleus RadioPharma and a former FDA commissioner in President Donald Trump’s first administration (December 2019–January 2021).
- Brett Giroir, MD, CEO of Altesa Biosciences; previously assistant secretary for health in Trump’s first term and an acting FDA commissioner (2019).
- Sara Brenner, MD, HHS senior counselor for public health as of April 16; previously FDA principal deputy commissioner and acting FDA commissioner (January–April 2025).
- Houman Hemmati, MD, PhD, a board-certified ophthalmologist and co-founder of Optigo Biotherapeutics, who is under consideration for CBER director.
- Richard Pazdur, MD, a 26-year FDA veteran who retired in December 2025 after serving three weeks as CDER director (November–December 2025); previously founding director, FDA Oncology Center of Excellence (2017–2025).
“If Makary’s ouster indeed stemmed from political disagreements (vapes, abortion), the next Commissioner could harbor more ideological views—which could compromise perceived Agency credibility—and just by virtue of having another change, this would likely exacerbate the mixed messages companies have been receiving around FDA’s bar for their drugs, one of the key regulatory challenges the sector has faced,” Abrahams cautioned.
Leaders and laggards
- Innate Pharma (Euronext Paris: IPH) shares jumped 35% from €1.23 ($1.42) to €1.66 ($1.92) on Wednesday after the Marseille, France-based developer of cancer drugs based on innate immunity and antibody engineering reported first-quarter results that beat analyst expectations. Innate finished Q1 with earnings per share of -0.1522, vs. the consensus forecast of -0.1616, on revenue of €2.6 million ($3.022 million) that was more than double (117% above) the €1.2 million ($1.395 million) reported in Q1 2025, thanks to partial or entire recognition of the proceeds received under collaboration agreements with AstraZeneca (NYSE, London Stock Exchange, and NASDAQ Stockholm: AZN) and Sanofi (Euronext Paris: SAN). Innate’s American depositary shares (ADSs) (NASDAQ: IPHA) rocketed 64% from $1.32 to $2.17 Wednesday.
- Reviva Pharmaceuticals Holdings (NASDAQ: RVPH) shares plummeted 56% from 80 cents to 35 cents on Wednesday after the central nervous system (CNS), inflammatory, and cardiometabolic disease drug developer disclosed in a regulatory filing that the Nasdaq Hearings Panel had delisted the company’s stock, suspending it from trading on the exchange as of Thursday. Reviva said its shares will instead begin trading that day on the OTCQB Venture Market under its existing symbol. The Panel told Reviva that it failed to comply with Nasdaq’s minimum bid price of $1 per share required for continued listing on the Nasdaq Capital Market. Reviva disclosed the delisting the same day it reported first quarter results: The company narrowed its quarterly net loss year-over-year, finished Q1 with a net loss of approximately $3.2 million ($0.46 per share) vs. approximately $6.4 million ($2.61 per share) in the year-ago quarter.
The post StockWatch: Regenxbio Tumbles Despite Positive Pivotal Data for DMD Gene Therapy Candidate appeared first on GEN – Genetic Engineering and Biotechnology News.
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