miRagen Therapeutics Presents New Data from Phase 1 Clinical Trial Evaluating MRG-106 in Subjects with Mycosis Fungoides MRG-106 has been generally well-tolerated; Improvements in disease severity demonstrated and genera

miRagen Therapeutics Presents New Data from Phase 1 Clinical Trial Evaluating MRG-106 in Subjects

with Mycosis Fungoides

MRG-106 has been generally well-tolerated;

Improvements in disease severity demonstrated and generally sustained through duration of therapy

BOULDER, CO, June 5, 2017 miRagen Therapeutics, Inc. (NASDAQ: MGEN), a clinical-stage biopharmaceutical company focused on the discovery

and development of RNA-targeted therapies, today announced new interim results from its ongoing Phase 1 clinical trial evaluating the safety, efficacy and pharmacokinetics of MRG-106 in subjects with the mycosis fungoides (MF) form of cutaneous

T-cell lymphoma (CTCL). The data were presented at the American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago.

consists of two parts. In the first part, from which results were previously reported, subjects were injected with 75 mg of MRG-106 directly into a specific lesion. The second part employed a dose-escalation design to evaluate 300 mg, 600 mg or 900

mg subcutaneous or intravenous administrations of MRG-106. A total of 19 subjects have been dosed over a period of one to 34 weeks and were evaluated based on a Composite Assessment of Index Lesion Severity (CAILS) score, which assesses the

severity of one or more lesions on a subject, and/or the modified Severity Weighted Assessment Tool (mSWAT) score, which assesses the severity of skin disease over a subject s entire body. Two subjects participated in both the first and second

A summary of results reported at ASCO from this first-in-human trial includes the following:

MRG-106 is an inhibitor of microRNA-155. In CTCL, as well as certain other blood cancers, microRNA-155 is present at abnormally high levels, and may play a

role in the proliferation of blood and lymph cells. miRagen believes therapeutic inhibition of microRNA-155 may reduce aberrant cell proliferation and the tumor growth characteristic of certain types of cancer.

We believe the enduring responses seen in this Phase 1 clinical trial of MRG-106 show potential for subjects with MF and other cancers where

microRNA-155 is found at abnormally high levels, said Paul Rubin, M.D., miRagen s Executive Vice President of Research and Development. While preliminary, the improvements appear to correlate with time on MRG-106 treatment, and the

results trends suggest that longer duration of treatment could result in greater efficacy.

We are pleased to present the new data at

the ASCO Annual Meeting from our MRG-106 Phase 1 clinical trial, which indicated that the product candidate has been generally well-tolerated to date. We believe the data presented support MRG-106 s intended mechanism of action and provide

an example of our foothold clinical development strategy, said miRagen President and CEO William S. Marshall, Ph.D. We look forward to the continued development of MRG-106 for the potential treatment of MF and believe the experience

gained in developing MRG-106 for MF may also allow us to address other indications where microRNA-155 is implicated in disease.

miRagen Therapeutics, Inc. is a clinical-stage biopharmaceutical company discovering and developing proprietary RNA-targeted

therapies with a specific focus on microRNAs and their role in diseases where there is a high unmet medical need. miRagen s two lead product candidates, MRG-106 and MRG-201, are currently in Phase 1 clinical trials. miRagen s clinical

product candidate for the treatment of certain cancers, MRG-106, is an inhibitor of microRNA-155, which is found at abnormally high levels in several blood cancers. miRagen s clinical product candidate for the treatment of pathological

fibrosis, MRG-201, is a replacement for microRNA-29, which is found at abnormally low levels in a number of pathological fibrotic conditions, including cutaneous, cardiac, renal, hepatic, and pulmonary

fibrosis, as well as systemic sclerosis. In addition to miRagen s clinical programs, it is developing a pipeline of pre-clinical product candidates. The goal of miRagen s translational medicine strategy is to progress rapidly to first in

human studies once it has established the pharmacokinetics, pharmacodynamics and safety of product candidates in pre-clinical studies. For more information, please visit www.miragenrx.com.

For information on clinical trials please visit www.clinicaltrials.gov.

Note Regarding Forward-Looking Statements

This press release may contain forward-looking statements that involve substantial risks and uncertainties for purposes of the safe harbor provided by the

Private Securities Litigation Reform Act of 1995. All statements contained in this press release other than statements of historical fact, including statements regarding miRagen s strategy, future operations, future financial position, future

revenue, projected expenses, prospects, plans and objectives of management or the expected features of or potential indications for miRagen s product candidates are forward-looking statements. The words believe, may,

will, estimate, continue, anticipate, intend, plan, expect, predict, potential, opportunity, goals, or

should, and similar expressions are intended to identify forward-looking statements. Such statements are based on management s current expectations and involve risks and uncertainties. Actual results and performance could differ

materially from those projected in the forward-looking statements as a result of many factors, including, without limitation: that miRagen has incurred losses since its inception, and anticipates that it will continue to incur significant losses for

the foreseeable future; future financing activities may cause miRagen to restrict its operations or require it to relinquish rights; miRagen may fail to demonstrate safety and efficacy of its product candidates; miRagen s product candidates are

unproven and may never lead to marketable products; miRagen s product candidates are based on a relatively novel technology, which makes it difficult to predict the time and cost of development and of subsequently obtaining regulatory approval,

if at all; miRagen s product candidates may cause undesirable side effects or have other properties that could delay or prevent the regulatory approval; and results of miRagen s Phase 1 clinical trials are not sufficient to show

safety and efficacy of miRagen s product candidates and may not be indicative of future clinical trial results.

miRagen has based these

forward-looking statements largely on its current expectations and projections about future events and trends. These forward-looking statements are subject to a number of risks, uncertainties and assumptions, including those described under the

heading Risk Factors in miRagen s Annual Report on Form 10-K and subsequent periodic reports filed with the Securities and Exchange Commission. Moreover, miRagen operates in a very

competitive and rapidly changing environment. New risks emerge from time to time. It is not possible for its management to predict all risks, nor can it assess the impact of all factors on its business or the extent to which any factor, or

combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements it may make. In light of these risks, uncertainties and assumptions, the future events and trends discussed in this press

release may not occur and actual results could differ materially and adversely from those anticipated or implied in the forward-looking statements. miRagen undertakes no obligation to revise or publicly release the results of any revision to such

forward-looking statements, except as required by law. Given these risks and uncertainties, readers are cautioned not to place undue reliance on such forward-looking statements. All forward-looking statements are qualified in their entirety by this

cautionary statement.

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