Today ProKidney announced that it had achieved statistical significance with respect to Group 1 of the ongoing phase 2 REGEN-007 study, which was evaluating the use of its autologous cell therapy rilparencel to treat patients with chronic kidney disease (CKD) and type 2 diabetes (T2D). The company’s stock closed the day higher by 515% to $3.73 on the back of this news. This cohort, or portion of the trial, is what ultimately likely caused the stock to finish the day higher. This, in spite of the fact that patients given this therapy in the second cohort (Group 2) did not reach statistical significance. The truth is that this was not a very easy study for it to work on either.
The reason why is because these were very sick patients. These were CKD patients with diabetes who had an estimated glomerular filtration rate (eGFR) of 20-50 mL/min/1.73 m. In essence, these were moderate-to-severe CKD patients who were recruited into this trial. A total of 49 patients were randomized to be in either Group (arm) of this study and then either given rilparencel or placebo. It is important to note, however, that there were two arms of this study, because this is actually what saved the company’s stock from trading lower after the release of data. Starting with the bad news, Group 2 (second arm) of the study showed that the drug was able to allow patients to see an eGFR slope improvement of 50%, which was not statistically significant. Thus, the p-value ended up being p=0.085.
The finding here was negative, but at least it was noted that there was a dose response with this arm of the mid-stage study. The good news from the trial came from that of Group 1, whereby 24 patients achieved an eGFR slope improvement of 78%. This improvement was said to be statistically significant on this endpoint with a p-value of p<0.001. The reason for the stock still trading higher, despite the disappointing data from Group 2, is because there already exists an ongoing phase 3 trial using rilparencel to treat patients with T2D and CKD known as PROACT 1. Furthermore, this late-stage trial incorporates the dosing regimen of Group 1 in the phase 2 study, whereby patients received two doses of this autologous cell therapy (one dose injected into each kidney 3 months apart).
Whereas, patients in Group 2 were only given 1 injection of rilparencel and then only given another injection in the other kidney if warranted to do so. The point here being that since the phase 3 PROACT 1 trial is designed in a similar fashion to Group 1 of the phase 2 REGEN-007 study, then the logical conclusion is that it should also see statistical significance when it comes to final eGFR slope improvement data. This win, though, is only half the battle, because the company definitely did prove that its cell therapy performed well in terms of improving eGFR function in the kidneys. However, it now has to meet with the FDA in order to see if it can use eGFR slope as a surrogate endpoint marker to file for Accelerated Approval of rilparencel to treat these T2D and CKD patients.
With that being said, the next catalyst to look forward to would be the conclusion of an expected FDA Type B meeting to take place during the summer, where the company will state its case on using this for such Accelerated Approval. The premise here is that the FDA might allow eGFR slope as a surrogate endpoint marker for a quicker pathway to approval, but in the end the U.S. agency is likely going to either want to see a confirmatory study or for the company to meet another primary efficacy endpoint to maintain approval (should it be granted accelerated approval on the surrogate endpoint noted). Besides the FDA Type B meeting as a milestone to look forward to, the company is expected to release full results from the mid-stage REGEN-007 study at the American Society of Nephrology (ASN) 2025 Kidney Week in terms of it as a late-breaking clinical trial.
This particular medical conference is expected to take place between November 5th – 9th of 2025 in Houston, Texas. The mechanism of action (MOA) of rilparencel is quite interesting, to say the least. The way it works is that a biopsy sample of the kidney disease is taken from the patient and then sent to the manufacturing lab of ProKidney. There, the cells that were collected are then expanded, and the cells that are selected are the ones that end up being put into the personalized cell therapy treatment. Once these cells are injected into the kidneys of the patient, they work to stabilize kidney functions in hopes of keeping the patient’s kidneys working in good order.
This point was proven in Group 1, whereby there was an improvement of eGFR slope by 78%. A high eGFR rate is good and indicates that the kidneys are working better. Thus, going from -5.8 mL/min/1.73m2 at the point of pre-injection compared to -1.3 mL/min/1.73m2 at the time of the final injection proves the MOA. This ended up being a 4.6 mL/min/1.73m2 improvement of eGFR slope, and thus, the statistical significance that was achieved with respect to this group of the phase 2 REGEN-007 trial. The hope is that this can be replicated in the larger phase 3 PROACT 1 trial, but this remains to be seen.