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RP-A501 (AAV9.LAMP2B)

Danon disease

Regulatory submission
BLA planned for late 2028
Last updated
300 sources

Product information and disease descriptionProduct descriptionProduct informationPharmacology

Pharmacodynamics

20 evidence topics · 19 sources

Preclinical pharmacology: dose-dependent LAMP2B protein restoration in the Lamp2 knockout mouse

“Lamp2 KO mice receiving AAV9.LAMP2B demonstrated dose-dependent restoration of human LAMP2B protein in the heart, liver, and skeletal muscle tissue.” (opens the source at this quote in a new tab)

“The mice were intravenously injected with phosphate-buffered saline (PBS) or AAV9.LAMP2B at doses of 1 × 10¹³, 5 × 10¹³, 1 × 10¹⁴, or 2 × 10¹⁴ vector genomes (vg)/kg.” (opens the source at this quote in a new tab)

“Administration of AAV9.LAMP2B resulted in dose- dependent expression of LAMP2 transcript in cardiac tissue from injected Lamp2 KO mice, with more than a 20-fold increase in LAMP2 expression in the 5 × 10¹³, 1 × 10¹⁴, and 2 × 10¹⁴ vg/kg doses compared with WT endogenous amounts (Fig. 1B).” (opens the source at this quote in a new tab)

Preclinical pharmacology: restoration of autophagic flux

“Impaired autophagic flux, evidenced by increased LC3-II, was abrogated by LAMP2B gene transfer in all tissues in both cohorts.” (opens the source at this quote in a new tab)

“Administration of AAV9.LAMP2B was associated with a dose-dependent reduction in LC3-II compared with PBS- injected mice as measured by Western blot.” (opens the source at this quote in a new tab)

“Autophagic structures were noted throughout the cytosol of un- treated LAMP2B KO (arrows in Fig. 1G); these findings were not noted in AAV9.LAMP2B-injected Lamp2 KO mice or WT controls.” (opens the source at this quote in a new tab)

Preclinical pharmacology: cardiac contraction and relaxation in treated mice

“Cardiac contraction and relaxation as evaluated by dP/dt max, dP/dt min (positive and negative first derivatives for maximal rates of left ventricular pressure development, respectively), and Tau (left ventricular relaxation time constant) were improved in a dose-dependent manner up to 2 × 10¹⁴ vg/kg in the AAV9.LAMP2B-treated Lamp2 KO mice compared with PBS-injected controls at all doses tested (Fig. 1, H and I, and table S5A) but are still different than WT mice.” (opens the source at this quote in a new tab)

“Cardiac contractility and relaxation as evaluated by dP/dTmax and dP/dTmin were also improved in a dose-dependent manner in the AAV9.LAMP2B treated LAMP2 KO mice compared to PBS controls.” (opens the source at this quote in a new tab)

“Kaplan Meier survival curve shows increased survival rate with higher doses of AAV9.LAMP2B.” (opens the source at this quote in a new tab)

Preclinical pharmacology: survival in treated mice

“Survival was also higher in the older cohort receiving high vector doses.” (opens the source at this quote in a new tab)

“In this study, Lamp2 KO mice receiving AAV9.LAMP2B at doses of 5 × 10¹³, 1 × 10¹⁴, and 2 × 10¹⁴ vg/kg in the 6-month-old cohort showed increased survival compared with PBS-injected controls (fig. S11A); however, the cause of death could not be ascertained.” (opens the source at this quote in a new tab)

“On the contrary, the mice from the 2-month-old cohort did not show difference in mortality by the time of sacrifice (fig. S11B).” (opens the source at this quote in a new tab)

Preclinical pharmacology: threshold dose for cardiac efficacy in the mouse model

“Ultimately, little difference was noted between the 1 × 10¹⁴ and 2 × 10¹⁴ vg/kg doses, suggesting that 1 × 10¹⁴ vg/kg may be a threshold dose for efficacy, although it is uncertain whether this will translate to human studies.” (opens the source at this quote in a new tab)

“✓ AAV9.LAMP2B confers direct benefit to cardiac function and improves ultrastructure at doses of 5×10¹³ vg/kg and higher in the LAMP2 KO mouse model” (opens the source at this quote in a new tab)

Preclinical pharmacology: durability of transgene expression in mouse myocardium

“No changes in VCN and LAMP2 mRNA transcripts were seen between 12 and 24 weeks after injection (fig. S4, A and B), indicating the persistence of the vector genomes and sustained transgene expression in the heart.” (opens the source at this quote in a new tab)

“The data also demonstrate persistent treatment effects up to 6 months after injection, indicating the durability of the therapy.” (opens the source at this quote in a new tab)

Preclinical pharmacology: hepatic and skeletal muscle effects in the mouse model

“AAV9.LAMP2B injection reduced serum ALP and ALT compared with PBS-injected Lamp2 KO mice (Fig 3, G and H). ALP and ALT were reduced by 51 and 64% in 1 × 10¹³ vg/kg, 54 and 59% in 5 × 10¹³ vg/kg, 50 and 76% in 1 × 10¹⁴ vg/kg, and 44 and 57% in 2 × 10¹⁴ vg/kg treated KO mice, suggesting a reduction in liver damage with treatment.” (opens the source at this quote in a new tab)

“Overall, AAV9. LAMP2B transduction was less extensive in the skeletal muscle compared with the heart or liver.” (opens the source at this quote in a new tab)

Limitations of the mouse model for pharmacodynamic assessment

“One of the limitations of the DD mouse model is the lack of detectable cardiac hypertrophy or reduction in ejection fraction (14).” (opens the source at this quote in a new tab)

“These mice do not develop reduced ejection fraction, even with intermittent starvation.” (opens the source at this quote in a new tab)

“The Lamp2 KO model used also does not develop significant fibrosis in the heart.” (opens the source at this quote in a new tab)

Preclinical pharmacology: transgene protein expression in non-human primate heart

“➢ Higher levels of transgenic human LAMP2 protein detected over endogenous NHP LAMP2 in most tissues tested, specifically the heart” (opens the source at this quote in a new tab)

“✓ AAV9.LAMP2B effectively transduces the heart (key target organ for DD). High VCNs, mRNA, as well as protein were noted in cardiac tissue of dosed mice and NHPs” (opens the source at this quote in a new tab)

“RP-A501 conferred high vector copy number (VCN) and LAMP2 protein expression in all four heart chambers, suggesting optimal tropism and uptake of the gene therapy.” (opens the source at this quote in a new tab)

“Importantly, protein expression in all four heart chambers was higher in treated non-human primates versus wild type; this differential was most pronounced in cardiac muscle.” (opens the source at this quote in a new tab)

Human induced pluripotent stem cell cardiomyocyte models: rescue by LAMP2B replacement

“Finally, gene correction of LAMP-2 mutation rescues the Danon phenotype.” (opens the source at this quote in a new tab)

“Correction of the LAMP-2 mutation in Danon hiPSC-CMs restores normal autophagy and mitochondrial function, as well as improves contractility.” (opens the source at this quote in a new tab)

“LAMP-2 OE iPSC-CMs exhibited an increase in the number of mature AVs ( Fig. 2D, E ) ( p <0.01) and a reduction in LC3-II levels ( Fig. 2H, I , Supporting Information Fig. 7C, D ) ( p <0.01) compared to Danon A2 iPSC-CMs indicating that reintroduction of LAMP-2 could rescue autophagic maturation.” (opens the source at this quote in a new tab)

“LAMP-2 OE iPSC-CMs showed calcium decay times near WT levels, indicating a rescue of the pathophysiologic phenotype ( Fig. 3G , Supporting Information Fig. 8B ).” (opens the source at this quote in a new tab)

“Interestingly, mitophagy can be rescued providing functional LAMP-2b[7].” (opens the source at this quote in a new tab)

Mouse bridging data for the recalibrated 3.8 × 10¹³ GC/kg dose

“Nonclinical bridging data further support the pharmacologic activity of the recalibrated dose. In a Danon disease mouse model, administration of Phase 2 material at 3.8 × 10¹³ GC/kg resulted in cardiac LAMP2B protein expression comparable to that observed at a higher dose and demonstrated comparable vector biodistribution.” (opens the source at this quote in a new tab)

Human pharmacodynamic markers assessed in the clinical program

“LAMP2 gene expression in endomyocardial biopsy samples is measured via both immunohistochemistry and Western blot and confirms the presence of LAMP2 protein in DD cardiac tissue following RP-A501 treatment.” (opens the source at this quote in a new tab)

“Histologic examination of endomyocardial biopsies via hematoxylin and eosin histology and electron microscopy is used to detect evidence of DD-associated tissue derangements, including the presence of autophagic vacuoles and disruption of myofibrillar architecture, each of which are characteristic of DD-related myocardial damage.” (opens the source at this quote in a new tab)

“High sensitivity troponin I or hs-TnI and BNP are blood-based evaluations and a key marker of HF and cardiac injury. Both are frequently elevated in DD patients and have been shown to be markedly elevated in patients with advanced stage disease.” (opens the source at this quote in a new tab)

Grading scale for myocardial LAMP2 protein expression by immunohistochemistry

“Grading of LAMP2 protein expression by IHC was done by a board-certified pathologist in a bl inded fashion. The semi-quantitative grading reflects the extent of LAMP2 protein expressing cardiomyocytes in the entirety of biopsy sample according to the scale.” (opens the source at this quote in a new tab)

“= Grade 3 (51%–74%) = Grade 4 (≥75%) Legend: IHC Staining Grade¶ (% Positive Cardiomyocytes) Grade 0 = no staining = Grade 1 (≤25%) NP = not performed = Grade 2 (26%–50%)” (opens the source at this quote in a new tab)

Myocardial LAMP2B protein expression by immunohistochemistry in the phase 1 adult cohorts, week 8 and month 12
Cohort and participantDoseWeek 8Month 12
Adult low dose, 1001“6.7 x 10¹³ GC/kg”“7.3%”“2.5% (Previously <15%)”
Adult low dose, 1002“6.7 x 10¹³ GC/kg”“36.9%”“67.8%”
Adult low dose, 1005“6.7 x 10¹³ GC/kg”“17.6%”“92.4%”
Adult high dose, 1006“1.1 x 10¹⁴ GC/kg”“5.0%”“100%”
Adult high dose, 1007“1.1 x 10¹⁴ GC/kg”“6.9%”“100%”

“Endomyocardial biopsies stained for LAMP2 compared to normal control samples. Percent area of cell staining was quantitated using software in a blinded fashion from 2 to 14 sections. Qualitative assessment reported for samples with high variance.” (opens the source at this quote in a new tab)

Myocardial LAMP2B protein expression by Western blot in the phase 1 adult cohorts
Cohort and participantWeek 8Month 5 to 18
Adult low dose, 1001“20.7%”“17.9%”
Adult low dose, 1002“27.3%”“21.2%”
Adult low dose, 1005“42.8%”“61.1%”
Adult high dose, 1006“14.6%”“18.2%”
Relationship between immunomodulation compliance and myocardial transgene expression

“In two of the three patients in the low dose cohort who had closely monitored compliance with the immunosuppressive regimen, high levels of cardiac LAMP2B expression were observed along with clinical biomarker improvements.” (opens the source at this quote in a new tab)

“Although we did observe evidence of cardiac LAMP2B expression of approximately 15% of cells compared to normal as determined by immunohistochemistry at 12 months in this patient, we believe that such expression was likely limited by inconsistent compliance with the immunosuppressive regimen, as evidenced by transient increases in transaminase levels approximately one month after treatment and a lack of adverse events frequently associated with the immunosuppressive regimen.” (opens the source at this quote in a new tab)

Dose relationship of myocardial LAMP2 expression: expression at the low dose and above

“On baseline endomyocardial biopsy, no pts had significant LAMP2B expression; 100% (N=6/6) of evaluable pts had cardiac LAMP2B expression within 6m of therapy with improved myocardial structure in 5/6.” (opens the source at this quote in a new tab)

“In Cohort 1 (N=3 pts, ≥15 y, 6.7 x 10¹³ GC/kg), RP-A501 increased cardiac LAMP2B expression by Western blot (WB) and immunohistochemistry (IHC) in myocardial tissue.” (opens the source at this quote in a new tab)

“The two pts in Cohort 1 with observed immunosuppressive regimen compliance had high cardiac LAMP2B expression: 67.8% and 92.4% vs. normal control by IHC; up to 61% by WB.” (opens the source at this quote in a new tab)

“Efficacy consistent in patients with Grade 1 vs. Grade >1 LAMP2 expression” (opens the source at this quote in a new tab)

Durability of myocardial LAMP2 protein expression and of vector-derived nucleic acid

“Durable myocardial LAMP2 protein expression seen in all patients” (opens the source at this quote in a new tab)

“Grade 0 LAMP2 protein IHC staining at the 30- and 36-month assessments, however, LAMP2B vector RNA and DNA (VCN) levels have persisted through 60 months of follow-up” (opens the source at this quote in a new tab)

“all evaluable Danon disease patients demonstrated LAMP2 protein expression at 12 months (sustained up to 60 months) and reduction of left ventricular (LV) mass index by ≥10% at 12 months (sustained up to 54 months) after treatment” (opens the source at this quote in a new tab)

“Preliminary long-term follow-up assessments for Patient 1001 were positive for immunohistochemical staining and appear to show Grade 3 expression in the heart at the five-year timepoint.” (opens the source at this quote in a new tab)

Pharmacodynamic response in myocardial tissue: reduction in autophagic vacuolar area

“Vacuolar area of endomyocardial tissue was quantified from H&E images. Data was quantified in a blinded manner using an AI tool.” (opens the source at this quote in a new tab)

“A. Data plotted for percentage vacuolar area of total tissue area from endomyocardial specimens pre- and post-gene therapy. B. Aggregate data indicating reduction across all cohorts.” (opens the source at this quote in a new tab)

“Restored Autophagy Sustained Following RP-A501” (opens the source at this quote in a new tab)

“Restored autophagy indicated by attenuation of vacuolar area” (opens the source at this quote in a new tab)

“Notably, all three patients showed visible improvements in autophagic vacuoles, a hallmark of Danon disease pathology, as assessed by electron microscopy of cardiac tissue via endomyocardial biopsy.” (opens the source at this quote in a new tab)

“Phase 1: LAMP2 expression associated with decreased vacuolar area, improved myofibrillar disarray, clinical improvement” (opens the source at this quote in a new tab)

Time to onset of the pharmacodynamic and structural response

“LAMP2 expression and LVMI improvements seen as early as 6 months post RP-A501” (opens the source at this quote in a new tab)

“Phase 1 trial: LAMP2 expression and LV Mass improvements seen as early as 6 months in pediatric subjects with updated immunomodulation regimen” (opens the source at this quote in a new tab)