The Src Kinase inhibition platform refers to novel, small molecule compounds having differentiated mechanisms of action (MOAs) including: (1) the inhibition of the activity of Src Kinase, and (2) the inhibition of tubulin polymerization.

The combination of these two mechanisms of action provides a broader range of anticancer activity compared to either mechanism of action alone. Our key clinical product candidates associated with the Src Kinase platform are tirbanibulin, formerly KX2-391 or KX-01) for actinic keratosis (AK), pre-cancerous lesions and psoriasis, and tirbanibulin oral for solid and liquid tumors.


Tirbanibulin ointment has shown promising results in actinic keratosis, or AK, a chronic and precancerous skin disease that occurs primarily in areas that have been exposed to ultraviolet (UV) radiation for a long period of time. It is usually found on the face, ears, lips, bald scalp, forearms, the posterior part of the hands, and lower legs. It is not possible to predict which AK lesions will develop into squamous cell carcinoma, so all lesions should be treated by a dermatologist. AK is the most common pre-cancerous dermatological condition and the second most common diagnosis made by dermatologists in the United States[1]. The reported prevalence of AK is between 11% and 25%[2].

The Company completed two pivotal, randomized, double-blind, vehicle-controlled Phase III trials (KX01-AK-003 and KX01-AK-004) that evaluated the efficacy and safety of tirbanibulin ointment 1% in 702 adults with actinic keratosis of the face or scalp. Tirbanibulin ointment 1% (10 mg/g) or vehicle (randomized 1:1) was self-administered to 25 cm2 of the face or scalp encompassing 4-8 typical AK lesions, once daily for 5 consecutive days. Both Phase III studies achieved their primary endpoint, which was defined as 100% clearance of the AK lesions at Day 57 within the face or scalp treatment areas, each study achieving statistical significance (p<0.0001) on this endpoint. In the KX01-AK-003 study, complete clearance was observed in 44% of the patients treated with tirbanibulin versus 5% for the vehicle treated groups. In the KX01-AK-004 study, complete clearance was observed in 54% of the patients treated with tirbanibulin and 13% for vehicle treated groups. Tirbanibulin demonstrated complete clearance of actinic keratosis lesions at day 57 in treated face or scalp areas in a significantly higher number of patients compared to vehicle. The most common adverse events were application site pruritus and pain reported by 9% and 10% of treated patients, respectively. The New England Journal of Medicine (NEJM) has published the results from the pivotal Phase III trials in the February 11, 2021 issue.

Tirbanibulin is also being investigated for the treatment of psoriasis. The trial has already yielded positive early signals of clinical activity, as disclosed in June 2019. Preclinical research is underway to identify further indications for tirbanibulin, such as skin cancers and other dermatological hyperproliferative disorders.

Tirbanibulin is also being developed as an oral for the control of cancer and hyper-proliferative disorders. Src plays a demonstrated role in regulating multiple aspects of tumor development, growth, and metastases, and its inhibition limits such tumor activity.

[1] Wilmer, EN, Gustafson CJ, Ahn CS, Davis SA, Feldman SR, Huang WW. Most common dermatologic conditions encountered by dermatologists and non-dermatologists. Cutis. 2014 Dec;94(6):285-92
[2] Stockfeth, E., Fernandiz, C, Grob JJ, et al., Development of a treatment algorithm for actinic keratoses: a European Consensus. Eur J Dermatol. 2008;18(6):651-659