Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Current assets:
Cash and cash equivalents	$ 9,671	$ 5,189
Accounts receivable	43	0
Inventory	37	37
Prepaid expenses and other current assets	5,163	3,751
Total current assets	14,914	8,977
Restricted cash	58	58
Operating lease right-of-use assets	2,753	3,073
Property and equipment, net	5,316	6,023
TOTAL ASSETS	23,041	18,131
Current liabilities:
Accounts payable	1,142	892
Accrued liabilities	2,482	5,002
Operating lease obligations, current portion	815	808
Notes payable, current portion	413	1,696
Convertible notes payable, current portion	0	2,378
Total current liabilities	4,852	10,776
Operating lease obligations, net of current portion	2,805	3,250
Notes payable, net of current portion	5,374	3,741
Convertible notes payable, net of current portion	12,937	9,800
TOTAL LIABILITIES	47,818	35,723
Commitments and contingencies (Note 9)
Stockholders’ deficit:
Common stock, $0.0001 par value: 600,000,000 shares authorized; 12,778,307 and 10,849,974 shares issued and outstanding at June 30, 2026 and December 31, 2025, respectively	1	1
Additional paid-in capital	304,825	290,531
Accumulated deficit	(329,811)	(308,296)
Accumulated other comprehensive income	208	172
TOTAL STOCKHOLDERS’ DEFICIT	(24,777)	(17,592)
TOTAL LIABILITIES AND STOCKHOLDERS’ DEFICIT	23,041	18,131
Common Stock Warrant Liability [Member]
Current liabilities:
Derivative liabilities	16,137	5,063
Derivatives Other Than Common Stock Warrants Liabilities [Member]
Current liabilities:
Derivative liabilities	$ 5,713	$ 3,093

Amount of convertible note payable as of the balance sheet date, classified as noncurrent.

No definition available.

Name:	clnn_ConvertibleNotePayableNoncurrent
Namespace Prefix:	clnn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).