Mersana Therapeutics Presents New Data on XMT-1536, a NaPi2b Targeting Antibody Drug Conjugate, at the AACR-NCI-EORTC International Conference
“The data presented at AACR-NCI-EORTC further support that NaPi2b is an outstanding target for ADC development and that the Dolaflexin ADC platform allows us to fully exploit the advantages of this interesting target,” said
The study revealed that XMT-1536 induced at least a 50% median reduction in tumor volume relative to baseline in 10/19 (53%) primary patient-derived ovarian cancer xenograft models, that were selected for testing without prior knowledge of NaPi2b expression status. The activity of XMT-1536 was comparable in models derived from tumors from treatment-naïve patients as well as models that came from patients with heavily pre-treated tumors. When NaPi2b target expression was evaluated using a proprietary immunohistochemistry (IHC) assay discovered at Mersana in conjunction with XMT-1536, there was an association between NaPi2b IHC H-score and tumor volume change after XMT-1536 treatment. Among tumors with an H-score ≥70, 10/12 (83%) of models achieved 50% or greater reduction in tumor volume after XMT-1536 treatment, vs. 0/7 (0%) models with an H-score ‹70. Applying the same IHC assay to primary human ovarian tumors, 12/20 (60%) tested tumors had an H-score ≥70, indicating the majority of human ovarian tumors express levels of NaPi2b associated with deep regressions in response to XMT-1536 in pre-clinical models.
“We are extremely pleased with the results of this research and the progress the program has made to date,” said
XMT-1536 is a highly potent anti-sodium-dependent phosphate transport protein (NaPi2b) immunoconjugate comprised of an average of 10-15 DolaLock payload molecules conjugated to XMT-1535, a proprietary humanized anti-NaPi2b antibody, via the Dolaflexin ADC platform. NaPi2b is an antigen highly expressed in the majority of non-squamous NSCLC and epithelial ovarian cancer. XMT-1536 is scheduled to begin Phase 1 clinical trials in early 2018.
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Source: Mersana Therapeutics, Inc.