Mesoblast (NASDAQ: MESO) completes enrollment in pivotal Phase 3 chronic low back pain study
Filing Impact
Filing Sentiment
Form Type
6-K
Rhea-AI Filing Summary
Mesoblast Limited reported that its pivotal Phase 3 trial of rexlemestrocel-L for chronic low back pain associated with degenerative disc disease has reached its patient recruitment target of at least 300 participants. Patients receive a single intra-discal injection of rexlemestrocel-L or sham control and are followed for 12 months.
The study aims to confirm earlier Phase 3 results that showed clinically meaningful pain and opioid-use reductions for up to three years. Top-line data are expected in mid-CY2027, with a planned U.S. FDA Biologics License Application filing in Q3 CY2027. Rexlemestrocel-L holds Regenerative Medicine Advanced Therapy designation, and Mesoblast sees potential peak year revenue above US$10 billion at single-digit market penetration, given over 7 million affected patients in the U.S.
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Insights
Mesoblast hit Phase 3 enrollment for a large chronic back pain program, moving closer to pivotal data and potential FDA filing.
Mesoblast has fully recruited its pivotal Phase 3 trial of rexlemestrocel-L in chronic low back pain due to degenerative disc disease, with at least 300 patients randomized to a single injection or sham control. The primary endpoint is pain reduction at 12 months, aligned with prior FDA agreement on approvable criteria.
The trial is designed to replicate earlier Phase 3 findings where a single injection yielded durable pain and opioid-use reductions for up to three years. Rexlemestrocel-L has Regenerative Medicine Advanced Therapy designation, which allows rolling review and eligibility for priority review once the Biologics License Application is filed.
Top-line results are expected in mid-CY2027, with an anticipated U.S. regulatory filing in Q3 CY2027. The company cites a U.S. addressable population above 7 million and potential peak year revenue over US$10 billion with single-digit penetration, underscoring the commercial stakes if efficacy and safety are confirmed.
Key Figures
Potential peak year revenue: >US$10 billion
U.S. CLBP prevalence: over 7 million people
Phase 3 sample size: at least 300 patients
+3 more
6 metrics
Potential peak year revenue
>US$10 billion
Estimated for chronic low back pain indication at single digit market penetration
U.S. CLBP prevalence
over 7 million people
Chronic low back pain due to inflammatory degenerative disc disease in the U.S.
Phase 3 sample size
at least 300 patients
Randomized to single intra-discal rexlemestrocel-L injection or sham control
Primary endpoint duration
12 months
Reduction in low back pain at 12 months versus sham control
Top-line data timing
mid-CY2027
Expected after last randomized patient completes 12-month follow-up
Planned FDA filing
Q3 CY2027
Intended timing for U.S. Biologics License Application submission
Key Terms
Regenerative Medicine Advanced Therapy (RMAT), Biologics License Application (BLA), allogeneic stromal cell therapy, chronic low back pain (CLBP), +1 more
5 terms
Regenerative Medicine Advanced Therapy (RMAT) regulatory
"Rexlemestrocel-L has Regenerative Medicine Advanced Therapy (RMAT) designation from the FDA"
A Regenerative Medicine Advanced Therapy (RMAT) is a U.S. regulatory designation for cell, gene and tissue-based treatments addressing serious or life-threatening conditions that shows early evidence of potential benefit. Think of it as a VIP lane with extra access to the regulator — more interaction, guidance and faster review — which can shorten development time and lower costs, making a program more valuable to investors, though it does not guarantee approval.
Biologics License Application (BLA) regulatory
"eligibility for priority review on filing of a Biologics License Application (BLA)"
A biologics license application (BLA) is a formal request to a government agency seeking approval to sell a biological medicine, such as vaccines or gene therapies, in the market. It is similar to a detailed report that proves the product is safe, effective, and manufactured properly. For investors, a BLA signifies a critical step toward commercial availability, often impacting a company's valuation and market prospects.
allogeneic stromal cell therapy medical
"its proprietary allogeneic stromal cell therapy targeting inflammatory processes underlying disc degeneration"
Allogeneic stromal cell therapy uses repair cells taken from a healthy donor and given to a different patient to help reduce inflammation and promote tissue healing. For investors, it matters because these off‑the‑shelf therapies can scale faster than patient‑specific treatments but face manufacturing, regulatory and immune‑reaction risks that affect clinical success, cost, and potential market size—think of buying a prebuilt repair crew versus training one each time.
chronic low back pain (CLBP) medical
"evaluating rexlemestrocel-L for the treatment of chronic low back pain (CLBP)"
Chronic low back pain (CLBP) is persistent or recurring pain in the lower back that lasts for months or longer, not just a short-term ache. It matters to investors because it drives steady demand for long-term treatments, devices, and care services and creates predictable healthcare spending and market opportunities; think of it like a recurring household repair that keeps generating costs and demand for better solutions.
degenerative disc disease (DDD) medical
"in patients with chronic low back pain (CLBP) due to inflammatory degenerative disc disease (DDD)"
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
Form 6-K
Report of Foreign Private Issuer
Pursuant to Rule 13a-16 or 15d-16 under the Securities Exchange Act of 1934
Pursuant to Rule 13a-16 or 15d-16 under the Securities Exchange Act of 1934
For the month of April 2026
Commission File Number 001-37626
Mesoblast Limited
(Exact name of Registrant as specified in its charter)
Not Applicable
(Translation of Registrant’s name into English)
Australia
(Jurisdiction of incorporation or organization)
(Jurisdiction of incorporation or organization)
Silviu Itescu
Chief Executive Officer and Executive Director
Level 38
55 Collins Street
Melbourne 3000
Australia
(Address of principal executive offices)
Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F:
Form 20-F ☑ Form 40-F ☐
INFORMATION CONTAINED ON THIS REPORT ON FORM 6-K
On April 29, 2026, Mesoblast Limited filed with the Australian Securities Exchange a new release announcement, which is attached hereto as Exhibit 99.1, and is incorporated herein by reference.
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly organized.
Mesoblast Limited | ||||||||||||||
| /s/ Paul Hughes | ||||||||||||||
| Paul Hughes | ||||||||||||||
| Company Secretary | ||||||||||||||
Dated: April 29, 2026
INDEX TO EXHIBITS
| Item | ||||||||
99.1 | Press release of Mesoblast Ltd, dated April 29, 2026. | |||||||
MESOBLAST ACHIEVES PATIENT RECRUITMENT TARGET IN PIVOTAL PHASE 3 TRIAL FOR CHRONIC LOW BACK PAIN New York, USA: April 28 and Melbourne, Australia: April 29, 2026: Mesoblast Limited (ASX:MSB; Nasdaq:MESO), global leader in allogeneic cellular medicines for inflammatory diseases, today announced that its pivotal Phase 3 clinical trial evaluating rexlemestrocel-L for the treatment of chronic low back pain (CLBP) associated with degenerative disc disease has achieved its patient recruitment target. This marks a significant milestone in Mesoblast’s plans for commercialization of rexlemestrocel- L, its proprietary allogeneic stromal cell therapy targeting inflammatory processes underlying disc degeneration. The placebo-controlled study (MSB-DR004) will follow at least 300 patients randomized to a single intra- discal injection of rexlemestrocel-L or sham control for 12 months. The trial seeks to confirm results from the earlier MSB-DR003 trial where a single intra-discal injection of rexlemestrocel-L resulted in clinically meaningful reductions in pain and opioid usage for up to three years. The trial’s primary endpoint is powered to show a significant difference in reduction of low back pain at 12 months between rexlemestrocel-L and sham controls. Secondary endpoints include improvements in function, quality of life, and cessation of pain medication, including opioids. Top-line results are expected in mid-CY2027 after the last randomized patient has completed follow-up. A positive readout will be used in support of an expected regulatory filing in Q3 CY2027 for United States Food and Drug Administration (FDA) approval. Rexlemestrocel-L has Regenerative Medicine Advanced Therapy (RMAT) designation from the FDA for treatment of CLBP due to degenerative disc disease providing eligibility for priority review once the Biologics License Application (BLA) has been filed. Silviu Itescu, Chief Executive of Mesoblast, said: “This is a major milestone toward delivering on our corporate goal of bringing to market a non-opioid, disease-modifying therapy for patients suffering from chronic low back pain, a condition with significant unmet medical need.” CLBP caused by inflammation and degenerative disc disease is a serious condition with a prevalence of over 7 million people in the U.S. alone. The indication is a potential blockbuster for Mesoblast with potential peak year revenue of >US$10 billion with single digit market penetration. About Rexlemestrocel-L for Chronic Low Back Pain associated with Degenerative Disc Disease The 300-patient randomized controlled confirmatory Phase 3 trial of Mesoblast’s second generation allogeneic, STRO3-immunoselected, and industrially manufactured stromal cell product candidate rexlemestrocel-L in combination with hyaluronic acid (HA) as delivery agent for injection into the lumbar disc is actively enrolling in patients with chronic low back pain (CLBP) due to inflammatory degenerative disc disease (DDD) of less than five years duration at multiple sites across the U.S. FDA has previously agreed on the design of this 300-patient randomized, placebo-controlled confirmatory Phase 3 trial, and the 12-month primary endpoint of pain reduction as an approvable indication. This endpoint was successfully met in Mesoblast’s first Phase 3 trial. Key secondary measures include improvement in quality of life and function. A particular focus is on treatment of patients on opioids, since discogenic back pain accounts for approximately 50% of prescription opioid usage in the US. Significant pain reduction and opioid cessation were observed in Mesoblast’s first Phase 3 trial. FDA has designated rexlemestrocel-L a Regenerative Medicine Advanced Therapy (RMAT) for the treatment of chronic low back pain. RMAT designation provides all the benefits of Breakthrough and Fast Track designations, including rolling review and eligibility for priority review on filing of a Biologics License Application (BLA). Exhibit 99.1
About Chronic Low Back Pain Back pain is the leading cause of disability in Americans under 45 years,1 with an annual prevalence in the general US adult population of 10-30%.2 CLBP caused by inflammation and degenerative disc disease (DDD) is a serious condition with a prevalence of over 7 million people in the US alone.3,4 CLBP due to DDD is a leading cause of disability, and is associated with impaired quality of life, severe limitations in ability to perform activities of daily living, reduced ability to work, and negative impacts on mental health. CLBP accounts for approximately 50% of prescription opioid usage in the US,5 making the condition a significant contributor to the opioid epidemic. About Mesoblast Mesoblast (the Company) is a world leader in developing allogeneic (off-the-shelf) cellular medicines for the treatment of severe and life-threatening inflammatory conditions. The therapies from the Company’s proprietary mesenchymal lineage cell therapy technology platform respond to severe inflammation by releasing anti-inflammatory factors that counter and modulate multiple effector arms of the immune system, resulting in significant reduction of the damaging inflammatory process. Mesoblast’s Ryoncil® (remestemcel-L-rknd) for the treatment of steroid-refractory acute graft versus host disease (SR-aGvHD) in pediatric patients 2 months and older is the first FDA-approved mesenchymal stromal cell (MSC) therapy. Please see the full Prescribing Information at www.ryoncil.com. Mesoblast is committed to developing additional cell therapies for distinct indications based on its remestemcel-L and rexlemestrocel-L allogeneic stromal cell technology platforms. Ryoncil® is being developed for additional inflammatory diseases including SR-aGvHD in adults and biologic-resistant inflammatory bowel disease. Rexlemestrocel-L is being developed for heart failure and chronic low back pain. The Company has established commercial partnerships in Japan, Europe and China. About Mesoblast intellectual property: Mesoblast has a strong and extensive global intellectual property portfolio, with over 1,000 granted patents or patent applications covering mesenchymal stromal cell compositions of matter, methods of manufacturing and indications. These granted patents and patent applications provide commercial protection extending through to at least 2044 in all major markets. About Mesoblast manufacturing: The Company’s proprietary manufacturing processes yield industrial-scale, cryopreserved, off-the-shelf, cellular medicines. These cell therapies, with defined pharmaceutical release criteria, are planned to be readily available to patients worldwide. Mesoblast has locations in Australia, the United States and Singapore and is listed on the Australian Securities Exchange (MSB) and on the Nasdaq (MESO). For more information, please see www.mesoblast.com, LinkedIn: Mesoblast Limited and Twitter: @Mesoblast References / Footnotes 1. American Academy of Pain Medicine - Get the Facts on Pain. The American Academy of Pain Medicine. http://www.painmed.org/patientcenter/facts-on-pain/ Accessed on June 28, 2017. 2. Urits I, Burshtein A, Sharma M, et al. Low Back Pain, a Comprehensive Review: Pathophysiology, Diagnosis, and Treatment. Current Pain and Headache Reports. 2019;23(3):1-10. doi:10.1007/s11916-019-0757-1. 3. Navigant: Commercial Assessment for a Proprietary Cell-Based Therapy for DDD in the U.S. and the EU3 – August 2014. 4. Decision Resources: Chronic Pain December 2015. Forward-Looking Statements This press release includes forward-looking statements that relate to future events or our future financial performance and involve known and unknown risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to differ materially from any future results, levels of activity, performance or achievements expressed or implied by these forward-looking statements. We make such forward-looking statements pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 and other federal securities laws. Forward-looking statements should not be read as a guarantee of future performance or results, and actual results may differ from the results anticipated in these forward-looking statements, and the differences may be material and adverse. Forward-looking statements include, but are not limited to, statements about: the initiation, timing, progress and results of Mesoblast’s preclinical and clinical studies, and Mesoblast’s research and development programs; Mesoblast’s ability to advance product candidates into, enroll and successfully complete, clinical studies, including multi-national clinical trials; Mesoblast’s ability to
advance its manufacturing capabilities; the timing or likelihood of regulatory filings and approvals, manufacturing activities and product marketing activities, if any; the commercialization of Mesoblast’s RYONCIL for pediatric SR-aGVHD and any other product candidates, if approved; regulatory or public perceptions and market acceptance surrounding the use of stem-cell based therapies; the potential for Mesoblast’s product candidates, if any are approved, to be withdrawn from the market due to patient adverse events or deaths; the potential benefits of strategic collaboration agreements and Mesoblast’s ability to enter into and maintain established strategic collaborations; Mesoblast’s ability to establish and maintain intellectual property on its product candidates and Mesoblast’s ability to successfully defend these in cases of alleged infringement; the scope of protection Mesoblast is able to establish and maintain for intellectual property rights covering its product candidates and technology; estimates of Mesoblast’s expenses, future revenues, capital requirements and its needs for additional financing; Mesoblast’s financial performance; developments relating to Mesoblast’s competitors and industry; and the pricing and reimbursement of Mesoblast’s product candidates, if approved. You should read this press release together with our risk factors, in our most recently filed reports with the SEC or on our website. Uncertainties and risks that may cause Mesoblast’s actual results, performance or achievements to be materially different from those which may be expressed or implied by such statements, and accordingly, you should not place undue reliance on these forward-looking statements. We do not undertake any obligations to publicly update or revise any forward-looking statements, whether as a result of new information, future developments or otherwise. Release authorized by the Chief Executive. For more information, please contact: Corporate Communications / Investors Paul Hughes T: +61 3 9639 6036 Media – Global Media – Australia Rubenstein BlueDot Media Caroline Nelson Steve Dabkowski T: +1 703 489 3037 T: +61 419 880 486 E: cnelson@rubenstein.com E: steve@bluedot.net.au
FAQ
What milestone did Mesoblast (MESO) announce in its chronic low back pain trial?
Mesoblast announced that it has achieved the patient recruitment target in its pivotal Phase 3 trial of rexlemestrocel-L for chronic low back pain. At least 300 patients are randomized to receive a single intra-discal injection of the cell therapy or sham control, with 12-month follow-up.
What is rexlemestrocel-L and what condition is Mesoblast targeting?
Rexlemestrocel-L is Mesoblast’s second-generation allogeneic stromal cell product combined with hyaluronic acid for lumbar disc injection. It targets chronic low back pain associated with inflammatory degenerative disc disease, aiming to reduce pain, improve function, and decrease opioid use versus sham control.
When does Mesoblast expect Phase 3 results and an FDA filing for rexlemestrocel-L?
Mesoblast expects top-line results from the pivotal Phase 3 chronic low back pain trial in mid-CY2027, after all patients complete 12-month follow-up. The company then plans to submit a Biologics License Application to the U.S. Food and Drug Administration in Q3 CY2027 for potential approval.
How large is the potential market for Mesoblast’s chronic low back pain therapy?
Mesoblast cites over 7 million people in the U.S. with chronic low back pain caused by inflammation and degenerative disc disease. Based on this population, the company describes the indication as a potential blockbuster, with possible peak year revenue above US$10 billion at single-digit market penetration.
What special FDA designation does rexlemestrocel-L have for chronic low back pain?
Rexlemestrocel-L has Regenerative Medicine Advanced Therapy (RMAT) designation from the U.S. Food and Drug Administration for chronic low back pain due to degenerative disc disease. RMAT provides benefits similar to Breakthrough and Fast Track, including rolling review and eligibility for priority review of a Biologics License Application.
What other products and indications is Mesoblast (MESO) developing?
Mesoblast develops allogeneic cellular medicines for severe inflammatory conditions. Its Ryoncil (remestemcel-L-rknd) is an FDA-approved mesenchymal stromal cell therapy for pediatric steroid-refractory acute graft versus host disease. The company is also developing remestemcel-L and rexlemestrocel-L for conditions like heart failure and inflammatory bowel disease.