Stephen Doberstein
Analyst · Cowen. Your line is open
Thank you, Howard. First, I'd like to outline how we analyze differences in the clinical performance between the lots. The majority of patients in PIVOT-02 rotated through different lots beyond cycle three of their treatment. So we focused our analysis on clinical differences based on the starting lots that our patient received. As of mid-May, approximately half of the patients in PIVOT began treatment with lots one and three, and half began treatment with lots two and five. We looked at differences in safety, first scan response and best objective response rate including complete response rate. In the particular cohorts of first-line melanoma, first-line renal cell carcinoma and first-line urothelial carcinoma we saw a correlation between improved clinical benefit in those patients who received lots one or three for their first dose, as compared to those who receive lots two or five for their first dose. This trend of improved clinical benefit was maintained even when analyzing these metrics by patient demographics baseline disease criteria or investigator sites. Given that the usage of the sub-optimal in-process intermediate was limited to only lots two and five, we combined the data for patients initially dosed with either lots two or five together and we combined the data for patients initially dosed with either lots two or five together and we combine the data for patients who started with in trend lots one or three together. First, let's start with safety. We observed no meaningful differences in safety between lots one and three and lots two and five, although some minor differences were observed and a directional trend towards more reported AEs did occur with lots one and three. Overall, the safety profile of the doublet continues to be well tolerated and is consistent with our prior data presentations. Starting now with the first-line melanoma cohort. As you'll recall, the best objective response rate as reported at ASCO 2019 for efficacy of valuable patients was 53% with a complete response rate of 34%. In addition, 42% of patients achieved 100% reduction in their target lesions. All 10 patients who were on treatment at the time of ASCO 2019 remain on treatment today or have achieved maximal clinical benefit in the study. As Howard stated, these data recently led to a breakthrough designation in first-line melanoma. Notably when you analyze this cohorts by combined lots for the 16 patients who started on lots one and three, the response rate at first scan was 56%. The response rate at first scan for the 22 patients who started on lots two and five was only 18%. The best objective response rate for lots one and three was 75% with a complete response rate of 44%. For lots two and five, the best objective response rate was 36% with a complete response rate of only 27%. As you'd imagine, these response differences also lead to an improvement in PFS seen between the lots. You'll recall that the overall patient population was at a median 12.7 months follow-up at ASCO 2019, and the median PFS was at a minimum of 12.7 months. When you break out those patients who started on lot one and three, median PFS can't yet be estimated because there are too few events of progressive disease. However, for patients who started on lots two and five, median PFS is estimated at 5.2 months and is reflected in a minimum median PFS of 12.7 months for the overall cohort. Notably 41% of the 22 patients who started on lots two and five experienced progressive disease at first scan. In the first-line urothelial cancer cohort, we now have 37 patients valuable for efficacy by investigator and we plan to present these data for this cohort at a future medical meeting. Since we first presented our urothelial cancer data at ASCO-GU, unfortunately 80% of new patient enrollments started treatments on lots two and five. Currently, the best ORR for the entire cohort is 38% with a complete response rate of 14%, there are still 13 patients with treatment ongoing in this cohort, of these, five have experienced complete responses and an additional five more patients could see further deepening of response. There are also four patients who are being treated beyond progression. When you analyze these data by lots, for the 12 patients who started on lots one and three, response at first scan was 42%. The response at first scan of the 25 patients who started on lot two and five was 32%. For patients who started on lots one and three, the best objective response rate was 50% with a complete response rate of 42%. For patients who started on lot two and five, the best objective response rate was only 32% and none of these patients had a complete response. These response differences also lead to an improvement in PFS for patients who started on lots one and three. PFS for the urothelial cohort is quite immature, but can be estimated at 4.1 months for the entire cohort, but when you examined by starting a lot, for patients who started on lots one and three median PFS can be estimated at 5.5 months, and for patients who started on lots two and five, median PFS is estimated at only 3.5 months. In the first-line renal cell carcinoma cohort, we currently have 49 patients are valuable for efficacy by investigator. Currently the best ORR for the whole cohort is 35% with a complete response rate of 4%, 11 patients remain on treatment in the RCC cohort. When you examine clinical performance by lot for the 25 patients who started on lots one and three, the response at first scan was 20%. For the 24 patients who started on lots two and five, the response at first scan was only 4%. The best objective response rate was 40% for patients starting on lots one and three, as compared to a best objective response rate of 29% for lots two and five. Median PFS is quite immature for the whole cohort, but is estimated at 7.6 months. When you analyze by lots for this cohort, median PFS for patients who started on lot one and three was only – was 11.2 months and PFS for patients who started on lot two and five was only 5.5 months. In first-line non-small cell lung cancer, when we examine the first scan depth of tumor reduction split by lots, there is some early evidence that the 16 patients who started on lots one and three are experiencing a greater reduction in their target lesions than the 13 patients who started on lots two and five. However, the data are very immature in this cohort and we'll continue to monitor whether this trend continues as data mature and as more patients are enrolled. In other cohorts in pivot beyond the ones I've just described, we did observe some clinical differences between patients who started on different lots, however, the differences were not as notable as they were in the other first-line settings. As of the May 17th data cut, we did not meet the Fleming thresholds for the response rates for relapsed or refractory settings in PIVOT-02 and this has made it more difficult to discern any differences in these cohorts. However, there are similarities, for example, in the cohorts of second and third-line non-small cell lung cancer, the few responses we observed were in patients who started on lots one and three. In the second-line I-O naïve RCC cohort, over half the patients who started on lots two and five had progressive disease at first scan, as compared to only 16% who started on lots one and three. Before I hand the call back to Howard, I'd like to briefly comment on planned data presentations for the rest of the year. First in melanoma, despite the differences between patients who started treatment with lot two and five and PIVOT-02, we're pleased with the ongoing deepening of responses we've reported in the first-line melanoma cohort, we and BMS have submitted an abstract to present updated 18-month follow-up data at the 2019 SITC meeting. Second in triple-negative breast cancer, we have submitted an abstract to the upcoming CRI quadruplet meeting for this cohort, we intend to hold a webcast with a leading breast cancer expert to review these data during that meeting. Third RCC, we are planning to submit these data from this cohort for possible presentation at ESMO I-O in December. Fourth non-small cell lung cancer. In January of this year at the time of the JP Morgan Conference, we had 10 patients evaluable for efficacy with varying PD-L1 status across all three of our first-line non-small cell lung cancer PD-L1 expression sub-cohorts. Enrollment has been slower than we anticipated in these cohorts and there are a number of patients who were enrolled more recently in the second and third quarters. Overall the early data we're observing in these few patients in the first-line non-small cell lung cancer sub-cohorts support the bempeg mechanism of action and its potential benefit in the below 50% PD-L1 expressors and in the PD-L1 negative baseline patients. As you know, we've reported that effect in other tumor types as well. In the greater than 50% PD-L1 expression sub-cohort, we haven't seen this same benefit and we're trying to understand this observation in light of the manufacturing issue. As I just stated, when we examine the depth of tumor reduction by lots, there is some early evidence that patients may be benefiting more when started on lots one and three. We’re enrolling additional patients in the first-line non-small cell lung cancer cohorts and those patients are starting treatment with bempeg lots that are not lots two and five. As a result of the current immaturity of the data and the desire to continue to enroll more of first-line non-small cell lung cancer patients, we withdrew our accepted abstract for the upcoming ESMO meeting. We plan to present these first-line non-small cell lung cancer cohorts once the data are more mature. As you'll recall, our PROPEL study was designed to be a dose finding Phase 1 trial to evaluate pembrolizumab in combination with bempeg, bempeg in non-small cell lung cancer and other tumor types. As Howard stated earlier, lot five was almost fully utilized in PROPEL. Now the patients are starting on different bempeg lots in PROPEL, we plan to focus on enrolling first-line non-small cell lung patients into PROPEL and we're also evaluating different dose levels of bempeg in non-small cell lung cancer to ensure dose optimization. This will allow us to generate important data in first-line non-small cell lung cancer with the pembro and bempeg doublet. With respect to additional trials starting with other collaborators in bempeg, Pfizer and Nektar have finalized the Phase 1b/2 study in head and neck cancer and castration-resistant prostate cancer. This study will be initiating imminently and we'll evaluate various doublet and triplet combination with bempeg and Pfizer and Merck Serono's anti-PD-L1 patient avelumab, Pfizer's PARP inhibitor Talazoparib and Pfizer and Astellas' Enzalutamide. We're very excited to work with Pfizer on this because of the opportunity in these two solid tumor settings for bempeg, particularly in patients that with PD-L1 negative tumors. With that, I'll turn the call back over to Howard.