TECHNICAL FIELD

The present invention relates to an agent for treating retinal diseases.

BACKGROUND ART

Aged-related maculopathy which is one of retinal disease is the first causative disease of acquired blindness in adult in Europe and USA, and the fourth in Japan. Hereafter, due to the progression of the society's aging, it is thought the number of patients having aged-related maculopathy would increase around the world. Decrease of vision caused by this disease is the cause that significantly decreases the QOL of many patients. However, there is no effective treatment method at the moment.

Further, no oral therapeutic agent that suppresses or ameliorates progression or exacerbation of aged-related maculopathy, and the development is strongly awaited.

On the other hand, SGLT2 inhibitor agent is a therapeutic agent for diabetes that inhibits sodium/glucose co-transporter2 (SGLT2) that is specifically present in proximal renal tubules and performs reabsorption of glucose, and promotes glucose excretion from urine to show an antihyperglycemic action. Clinical application of six types of SGLT2 inhibitor agent has already been performed (see for example, non-patent documents 1, 2). However, it is not known that the SGLT2 inhibitor agent has a direct ameliorating effect on retinal diseases that is not cause by high blood sugar such as aged-related maculopathy.

PRIOR ART DOCUMENTS

Non-Patent Documents

Non Patent Document 1:

Bailey C J. Renal glucose reabsorption inhibitors to treat diabetes. Trends Pharmacil Sci 2011; 32:63-71
Non Patent Document 2:Zaccadi F, Webb D R, Htike Z Z, Youssef D, Khunti K, Davies M J. Efficacy and safety of sodium-glucose co-transporter-2 inhibitors in type 2 diabetes mellitus: systematic review and network meta-analysis. Diab Obes Metab 2016; 18:783-94

SUMMARY OF THE INVENTION

Object to be Solved by the Invention

The object of the present invention is to provide an agent for treating and/or ameliorating retinal diseases such as aged-related maculopathy.

Means to Solve the Object

The present inventors made a keen study on action effect of SGLT2 inhibitor agent as a therapeutic agent for diabetes showing antihyperglycemic action. First, the present inventors focused that with respect to the actual administration amount of SGLT2 inhibitor agent, only a tiny amount reaches the proximal renal tubules where the SGLT2 inhibitor agent acts, and then found out that the existing SGLT2 inhibitor agent has an effect of ameliorating retinopathy caused by glucose (retinopathy caused by high blood sugar), with an administration amount that shows an antihyperglycemic action, and with a low dosage administration which does not show an antihyperglycemic action (PCT/JP2016/86658).

The present inventors further advanced their studies, and found out that SGLT2 inhibitor agent shows a protecting effect in aged-related maculopathy mouse model that does not show high blood sugar. Specifically, it has been found out that SGLT2 inhibitor agent exerts an ameliorating effect with a mechanism of suppressing sodium and/or glucose intake even on aged-related maculopathy which is a completely different disease (retinal disease that is not caused by high blood sugar) that is not caused by an excessive inflow of glucose in retinal constituting cells by high blood sugar. The present invention has been thus completed.

Specifically, the present invention relates to the following.

[1] An agent for treating retinal disease not caused by high blood sugar, comprising sodium/glucose co-transporter2 inhibitor (SGLT2 inhibitor) as an active ingredient.

[2] The agent for treating according to [1], which is administered at a low dosage whereby no lowering in blood sugar is observed.

[3] The agent for treating according to [1] or [2], wherein the SGLT2 inhibitor is at least one selected from canagliflozin, ipragliflozin, dapagliflozin, luseogliflozin, empagliflozin and tofogliflozin.

[4] The agent for treating according to any one of [1] to [3], wherein the retinal disease not caused by high blood sugar is aged-related maculopathy.

Effect of the Invention

According to the therapeutic agent of the present invention, retinal diseases that are not caused by high blood sugar such as age-related maculopathy can be treated by administering SGLT2 inhibitor agent at an administration amount whereby lowering in blood sugar is observed, and also with a lower dosage whereby no antihyperglycemic action is observed. As the therapeutic agent of the present invention exerts an effect with an administration at a low dosage, there is no problem of hypoglycemia, excessive urination/frequent urination, anhydration, urinary tract infection/genital infection, and increase of ketone body, which are main side effects caused by action of promoting urine sugar elimination of the existing SGLT2 inhibitor agents, and the safety is significantly high. The therapeutic agent of the present invention enables to expand a new application as a therapeutic agent for age-related maculopathy, etc.

