Safety and Efficacy of Intravitreal Injection of Human Retinal Progenitor Cells in Adults With Retinitis Pigmentosa

Mean change in BCVA in study eye from baseline to month 12 as assessed by E-ETDRS in ITT population. A letter score is used to compare change over time, with a higher number of letters representing better visual function, and a lower number of letters representing worse visual function. For example, 85 letters is equivalent to 20/20 visual acuity and 5 letters is equivalent to 20/800 visual acuity. A change value is derived for each subject by taking the letter score at 12 months and subtracting the letter score at baseline. A mean of all change values is then calculated for each arm.

Assessment of the ability to detect changes in shades of grey, as measured with a vertical striped pattern that varies in width (cycles per degree or CPD); CS thresholds are created by taking the mean of multiple trials at each pattern width. A CS curve is created using a minimum of three pattern widths, one at the subject's peak or highest sensitivity, and then one larger and smaller pattern width on either side of the peak. For example, if a subject's CS peak appears to be at 2.0 CPD, then additional testing occurs at 1.0 and 4.0 CPD. RP patients have suppressed CS curves and the most common pattern widths are at 0.5, 1.0, 2.0, and 4.0 CPD. Severely impaired subjects (e.g., BCVA < 20/400) usually have flat curves with low values (e.g., 1.28), while in mildly impaired RP subjects the values can be higher (e.g., 7.12), but are rarely near normal. These data represent mean change in CS from baseline to 12 months, with greater values representing greater improvement in visual function.

Mean change in total area (degrees squared) of all islands of vision from baseline to 12 months.

The LLMT identifies the performance of RP patients as they walk along an indoor pathway of arrows and obstacles at varying lighting levels. The Critical Illumination Level (CIL) is the light level below which the patient has a markedly slower pace and more errors than all light levels above (brighter than) that point. The LLMT uses light levels that go from very dim (0.12 lux) to a bright indoor room (500 lux), with evenly spaced increments that increase light by doubling the brightness of the room from the prior level. These evenly spaced light levels have been converted to a scale score to enable easier calculation of change scores. The dimmest light level of 0 lux (completely dark room) corresponds to a scale score of 13, whereas the brightest light level of 500 lux corresponds to a scale score of 0. A positive scale score change from baseline to 12 months represents improvement in low light vision, whereas a negative scale score change represents a decline in low light vision.

The VA LV VFQ-48 (VFQ) is used to capture changes in patients' self-reporting of their difficulty with reading, mobility and performing other daily living activities affected by visual impairment. There are 4 scales on the VFQ including Visual Information, Reading, Visual Motor, and Mobility. A fifth value, Visual Ability, is an aggregate score of the 4 scales, measured in units called logits, and is calculated for each person based on item weighting using Raasch analysis. Visual Ability is used broadly to represent changes in subject-reported outcomes from visit to visit. Higher positive values on the Visual Ability score represent better function and less impairment, whereas lower or negatives scores represent worse function or more impairment. Change in the Visual Ability scale on the VFQ is calculated by taking a subject's score at 12 months and subtracting from it the baseline score.

Assessed by treatment emergent adverse events, immunogenicity and safety visual assessments