Additional P2b Data for MDNA55 Presented
On November 25, 2019, Medicenna Therapeutics Corp. (TSX:MDNA.TO) (OTC:MDNAF) announced the presentation of additional clinical data from the ongoing Phase 2b clinical trial of MDNA55, an IL-4 targeted toxin, in patients with recurrent glioblastoma (rGBM). The Phase 2b clinical trial enrolled a total of 46 rGBM patients experiencing their first or second GBM relapse (NCT02858895). It is a multi-center, open label, single arm study with the primary endpoint of median overall survival (mOS) and a secondary endpoint of objective response rate (ORR) following a single intra-tumoral infusion of MDNA55 in adult rGBM subjects.
The company provided an update based on a data cutoff of Oct. 31, 2019 that included an additional seven patients since the prior update in September 2019. The following chart shows the survival curve for the first 40 subjects evaluated, which includes a mOS of 11.6 months and OS at 12 months of 45%. Those numbers are in-line with what the company reported in September 2019.
Similar to what was reported in Sep. 2019, there continues to be a survival advantage for patients who are high expressers of the IL-4 receptor (IL-4R). The figure on the lower left shows that patients who have high levels of IL-4R have a mOS of 15.0 months, while those that have low levels of IL-4R have a mOS of 8.4 months. What is most interesting about this is the fact that published data shows GBM patients that have high expression of IL-4R have a lower mOS than patients who are low expressers of IL-4R (lower right), thus the fact that these patients are living longer in the Phase 2b trial is highly encouraging.
Medicenna also reported updated tumor control data for the 38 evaluable patients. The following figure shows tumor control from baseline, in which 19 of 38 (50%) evaluable patients saw either stabilization of the tumor or a decrease in tumor size.
While a 50% tumor control rate is certainly encouraging, we don’t believe the preceding chart gives a wholly accurate picture of MDNA55’s treatment effect due to pseudoprogression, in which a tumor appears to be growing on radiographic imaging (due to an inflammatory response to treatment and not due to an increase in tumor mass) before decreasing in size. To account for this phenomenon, assessment of tumor response from nadir was utilized using the criteria for immunotherapy Response Assessment in Neuro-Oncology (iRANO) (Okada et al., 2015). The following figure shows that 21 of 38 (83%) patients saw either stabilization of the tumor or a decrease in tumor size when compared to nadir.
There was also an association seen between tumor control and mOS, with those experiencing either tumor shrinkage or stabilization having a mOS of 15.2 months, those with pseudoprogression having a mOS of 12.0 months, and those with tumor progression only having a mOS of 8.4 months.
While a bit disappointing that the mOS data did not improve from the data reported in September 2019 following the addition of data for seven ‘high dose’ patients, treatment with MDNA55 continues to exceed previously reported mOS data for other rGBM treatments such as Avastin®, lomustine, and temozolomide.
Medicenna will continue to present updated data on the remaining patients from the Phase 2b trial at upcoming scientific conferences. We anticipate the company conducting an ‘end-of-Phase 2’ meeting with the FDA in the first quarter of 2020 to determine the regulatory path forward for MDNA55 and whether the opportunity exists for accelerated approval.
The additional data presented by Medicenna continues to compare quite favorably to currently available rGBM treatments and we look forward to additional updates on the remaining patients in the study, which is likely to occur at future scientific conferences. The upcoming ‘end-of-Phase 2’ meeting with the FDA is a potential inflection point as the company will learn what the agency will require in terms of a Phase 3 clinical trial and whether there is any potential for accelerated approval. Our current valuation is CAD$4.50 and we continue to view the shares as significantly undervalued heading into a very important next couple of months for the company.
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