Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Current assets:
Cash and cash equivalents	$ 7,285	$ 12,155
Accounts receivable	0	64
Inventory	79	68
Prepaid expenses and other current assets	4,621	3,870
Total current assets	11,985	16,157
Restricted cash	58	58
Operating lease right-of-use assets	3,373	3,643
Property and equipment, net	6,709	7,479
TOTAL ASSETS	22,125	27,337
Current liabilities:
Accounts payable	828	1,240
Accrued liabilities	5,359	7,766
Operating lease obligations, current portion	1,013	926
Notes payable, current portion	374	359
Total current liabilities	7,574	10,291
Operating lease obligations, net of current portion	3,706	4,132
Notes payable, net of current portion	4,619	4,610
Convertible notes payable	11,134	10,816
TOTAL LIABILITIES	30,675	36,194
Commitments and contingencies (Note 9)
Stockholders’ deficit:
Common stock, $0.0001 par value: 600,000,000 shares authorized; 9,462,071 and 8,089,565 shares issued and outstanding at June 30, 2025 and December 31, 2024, respectively	1	1
Additional paid-in capital	281,593	273,194
Accumulated deficit	(290,293)	(282,123)
Accumulated other comprehensive income	149	71
TOTAL STOCKHOLDERS’ DEFICIT	(8,550)	(8,857)
TOTAL LIABILITIES AND STOCKHOLDERS’ DEFICIT	22,125	27,337
Common Stock Warrant Liability [Member]
Current liabilities:
Derivative liabilities	2,546	4,541
Derivatives Other Than Common Stock Warrants Liabilities [Member]
Current liabilities:
Derivative liabilities	$ 1,096	$ 1,804

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).