The presentation of confirmatory data regarding the prevalence of the biomarker EB1 (end binding protein-1) in several cancer settings at ASCO is a reminder of the potential applicability of lisavanbulin across multiple cancer settings and the need to improve success rates in difficult to treat cancers.
The use of the biomarker EB1 is important in intractable cancers as Basilea seeks to enrich the patient population for patients who respond best to its novel spindle assembly checkpoint inhibitor lisavanbulin. Increasing the proportion of responders is important to the extent that it reduces failure rates and improves the likelihood of success.
While novel, there is a growing body of evidence regarding the importance of EB1 (along with its binding partners) inmicrotubule regulation. EB1 is a member of the plus-end tracking protein family which regulate microtubule dynamics. Previously, its cancer-causing potential has been associated with glioblastoma, oesophageal and breast cancer cell lines and overexpression has been reported in gastric, hepatic and oral cancers. As a result, EB1 expression should be a good predictive marker for microtubule targeting agents such as lisavanbulin. Data generated so far in a clinical proof-of-concept trial in glioblastoma patients has been highly encouraging with two EB1 positive patients experiencing profound responses.
The data presented at ASCO adds to this body of data and is important as Basilea seeks to identify appropriate tumour types and patients for lisavanbulin. The EB1 prevalence data presented at ASCO was based on 565 patient tissue samples from 14 different tumour types. The ongoing POC clinical study in glioblastoma seeks to capitalise on the ability of lisavanbulin to cross the blood brain barrier while enriching patients using EB1. The prevalence data presented confirmed earlier suggestions that circa 5% of glioblastoma patients express EB1. While this proportion may sound modest, this is a very challenging cancer and although rare, is highly malignant and incurable with a median survival time of 15-18 months.
Basilea also identified other cancers where EB1 may be an important predictive biomarker which included metastatic melanoma while slightly lower levels of EB1 staining were associated with NSCLC, as well as colorectal and triple-negative breast cancer. Outside of glioblastoma strong EB1 expression was associated with rare cancer types such as medulloblastomas and neuroblastomas suggesting further potential for lisavanbulin. An important insight into the relevance of EB1 and the activity of lisavanbulin in glioblastoma should be delivered by the ongoing proof of concept study. Interim results are anticipated towards the end of 2021.
Lisavanbulin currently sits outside of our financial model and valuation and represents an important source of upside should clinical data prove supportive.
We have calculated a discounted cash flow fair value of CHF 120 for Basilea. The current share price is CHF 43.9.
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Basilea Pharmaceutica is a client of Calvine Partners and as such, this publication is not independent and should be considered a marketing communication under FCA Rules. None of the information contained in this publication should be considered as any form of advice.