KX1-004

KX1-004 is a non-ATP competitive inhibitor of pp60c-src with IC50 value of 40 μM [1].

KX1-004 is a close analog of the indole-based Src-PTK inhibitors reported previously. It has a 5-fluoro group and showed potent inhibition activity in isolated Src-PTK assay. KX1-004 was found to have protective effect in noise-induced hearing loss. The chinchillas treated with 30 μM KX1-004 were exposed to continuous noise. And the results showed that treated ears exhibited up to 40 dB less threshold shift (TTS) and up to 25 dB less permanent threshold shift (PTS) than control ears. KX1-004 treatment also significantly reduced outer hair cell (OHC) loss than control. Besides that, KX1-004 was proved to reduce the hearing loss and hair cell loss associated with impulse noise exposure markedly [1, 2].

References:
[1] Harris K C, Hu B, Hangauer D, et al. Prevention of noise-induced hearing loss with Src-PTK inhibitors. Hearing research, 2005, 208(1): 14-25.
[2] Milkiewicz K L, Marsilje T H, Woodworth Jr R P, et al. The design, synthesis and activity of non-ATP competitive inhibitors of pp60 c-src tyrosine kinase. Part 2: Hydroxyindole derivatives. Bioorganic & medicinal chemistry letters, 2000, 10(5): 483-486.

A putative role of p53 pathway against impulse noise induced damage as demonstrated by protection with pifithrin-alpha and a Src inhibitor.[Pubmed:24472721]

Neurosci Res. 2014 Apr-May;81-82:30-7.

Exposure to high-level noise leads to oxidative stress and triggers apoptosis of the hair cells. This study examined whether p53, a tumor suppressor protein, is activated in the cochlea following impulse noise exposure. Inhibition of p53 with pifithrin alpha, a specific p53 inhibitor, or KX1-004, a Src-protein tyrosine kinase inhibitor, was tested to determine if p53 inhibition could reduce noise-induced hearing loss and cochlear damage. Chinchillas were pre-treated with a local administration of pifithrin alpha or KX1-004 and exposed to impulse noise. The chinchillas were assessed for threshold shift at 1 and 24h after the noise. At 4 or 24h post noise, the cochleae were removed and organs of Corti were examined to assess the damage to the cells and upregulation of p53 by the noise. Apoptosis was evident in both outer hair cells and supporting cells. Phospho-p53 (Ser 15) was upregulated 4h and 24h after the noise. KX1-004 and pifithrin alpha both decreased threshold shift and the number of missing outer hair cells. These results indicate that p53 is involved in the early stages of noise-induced cell death and inhibition of this signaling pathway is a potential protective strategy against noise-induced hearing loss.

Protection from impulse noise-induced hearing loss with novel Src-protein tyrosine kinase inhibitors.[Pubmed:21840347]

Neurosci Res. 2011 Dec;71(4):348-54.

Apoptosis is a significant mechanism of cochlear hair cell loss from noise. Molecules that inhibit apoptotic intracellular signaling reduce cochlear damage and hearing loss from noise. The current study is an extension of a previous study of the protective value of Src-protein tyrosine kinase inhibitors against noise (Harris et al., 2005). The current study tested three Src-inhibitors: the indole-based KX1-141, the biaryl-based KX2-329, and the ATP-competitive KX2-328. Each of the three drugs was delivered into the chinchillas' cochleae by allowing the solutions to diffuse across the round window membrane thirty minutes prior to exposure to impulse noise. Hearing thresholds were measured using auditory evoked responses from electrodes in the inferior colliculi. Ears treated with KX2-329 showed significantly lower threshold shifts and outer hair cell losses than the control group. The cochleae treated with KX1-141 and KX2-328 did not show statistically significant protection from the impulse noise. The finding of protection with KX2-329 demonstrates that a biaryl-based Src inhibitor has protective capacity against noise-induced hearing loss that is as good as that demonstrated by KX1-004, a Src inhibitor drug that has been studied extensively as an otoprotectant against noise, and suggests that KX2-329 could be useful for protection against noise.

Postexposure treatment with a Src-PTK inhibitor in combination with N-l-acetyl cysteine to reduce noise-induced hearing loss.[Pubmed:21768733]

Noise Health. 2011 Jul-Aug;13(53):292-8.

Both the antioxidant, N-l-acetyl cysteine (NAC), and the Src inhibitor, KX1-004, have been used to protect the cochlea from hazardous noise. In order to extend our previous work on KX1-004 with noise exposure, the current studies were undertaken with two goals: (1) to test the effectiveness of NAC and KX1-004 in combination with one another when given in a protection paradigm, and (2) to test the NAC+KX1-004 combination in a postexposure rescue paradigm. The noise exposure for the first experiment consisted of a 4-kHz octave band of noise at 107 dB SPL for 2 hours. The combination of NAC and KX1-004 were administered either prior to the noise exposure or post exposure (rescue). The second experiment was undertaken to extend the findings of the first experiment's rescue paradigm. The 4 kHz octave band noise was delivered at 112 dB SPL for 1 hour, with the experimental drugs delivered only in a rescue paradigm. In Experiment 1, animals treated before the 2-hour noise exposure with the combination of NAC and KX1-004 had from 12 to 17 dB less permanent threshold shift when compared to control saline treated animals. Treatment in the rescue paradigm did not produce any reductions in threshold shift from the 2-hour exposure. In the second experiment, with the 1-hour noise, rescue with KX1-004 or KX1-004 plus NAC yielded small, but significant, reductions in threshold shift. There was no additional benefit from the combination of NAC and KX1-004 over KX1-004 by itself.

A comparison of the protective effects of systemic administration of a pro-glutathione drug and a Src-PTK inhibitor against noise-induced hearing loss.[Pubmed:17478966]

Noise Health. 2005 Oct-Dec;7(29):24-30.

Both the antioxidant, n-l-acetyl cysteine (L-NAC) and the Src inhibitor, KX1-004, have been used to protect the cochlea from hazardous noise. To date, KX1-004 has only been used locally on the round window. In the current study, the two drugs were administered systemically. LNAC was delivered intraperitoneally at a dose of 325 mg/kg while KX1-004 was administered subcutaneously at a dose of 50 mg/kg. The noise exposure consisted of a 4 kHz octave band of noise at 100 dB SPL for 6 hours/day for 4 days. The drugs were administered once each day, 30 minutes prior to the onset of the noise exposure. The animals' hearing was estimated using the evoked response records from surgically-implanted chronic electrodes in the inferior colliculi. Animals treated with LNAC and KX1-004 had from 10 to 20 dB less temporary threshold shift at day 1 and an average 10 dB less permanent threshold shift by day 21 when compared to control saline treated animals. There were no significant side effects (i.e.: appetite loss, weight loss, lethargy, etc.) related to either of the drug treatments. KX1-004 produced at least as much protection as L-NAC, but at a significantly lower concentration.

Prevention of noise-induced hearing loss with Src-PTK inhibitors.[Pubmed:15950415]

Hear Res. 2005 Oct;208(1-2):14-25.

Studies from our lab show that noise exposure initiates cell death by multiple pathways [Nicotera, T.M., Hu, B.H., Henderson, D., 2003. The caspase pathway in noise-induced apoptosis of the chinchilla cochlea. J. Assoc. Res. Otolaryngol. 4, 466-477] therefore, protection against noise may be most effective with a multifaceted approach. The Src protein tyrosine kinase (PTK) signaling cascade may be involved in both metabolic and mechanically induced initiation of apoptosis in sensory cells of the cochlea. The current study compares three Src-PTK inhibitors, KX1-004, KX1-005 and KX1-174 as potential protective drugs for NIHL. Chinchillas were used as subjects. A 30 microl drop of one of the Src inhibitors was placed on the round window membrane of the anesthetized chinchilla; the vehicle (DMSO and buffered saline) alone was placed on the other ear. After the drug application, the middle ear was sutured and the subjects were exposed to noise. Hearing was measured before and several times after the noise exposure and treatment using evoked responses. At 20 days post-exposure, the animals were anesthetized their cochleae extracted and cochleograms were constructed. All three Src inhibitors provided protection from a 4 h, 4 kHz octave band noise at 106 dB. The most effective drug, KX1-004 was further evaluated by repeating the exposure with different doses, as well as, substituting an impulse noise exposure. For all conditions, the results suggest a role for Src-PTK activation in noise-induced hearing loss (NIHL), and that therapeutic intervention with a Src-PTK inhibitor may offer a novel approach in the treatment of NIHL.