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                             April 19, 2021

       Robert Spignesi
       President and Chief Executive Officer
       Rapid Micro Biosystems, Inc.
       1001 Pawtucket Boulevard West, Suite 280
       Lowell, MA 01854

                                                        Re: Rapid Micro
Biosystems, Inc.
                                                            Draft Registration
Statement on Form S-1
                                                            Submitted March 22,
2021
                                                            CIK No. 0001380106

       Dear Mr. Spignesi:

              We have reviewed your draft registration statement and have the
following comments. In
       some of our comments, we may ask you to provide us with information so
we may better
       understand your disclosure.

              Please respond to this letter by providing the requested
information and either submitting
       an amended draft registration statement or publicly filing your
registration statement on
       EDGAR. If you do not believe our comments apply to your facts and
circumstances or do not
       believe an amendment is appropriate, please tell us why in your
response.

             After reviewing the information you provide in response to these
comments and your
       amended draft registration statement or filed registration statement, we
may have additional
       comments.

       Draft Registration Statement on Form S-1

       General

   1.                                                   Please provide us with
copies of all written communications, as defined in Rule 405 under
                                                        the Securities Act,
that you, or anyone authorized to do so on your behalf, present to
                                                        potential investors in
reliance on Section 5(d) of the Securities Act, whether or not they
                                                        retain copies of the
communications.
       Prospectus Summary
       Overview, page 1

   2.                                                   Please expand your
disclosure on the top of page 2 to describe what a Form 483 is.
 Robert Spignesi
FirstName   LastNameRobert
Rapid Micro   Biosystems, Inc.Spignesi
Comapany
April       NameRapid Micro Biosystems, Inc.
       19, 2021
April 219, 2021 Page 2
Page
FirstName LastName
3.       We note your disclosure that your Growth Direct platform is the only
fully automated,
         high-throughput and secure MQC solution. We further note your
disclosure under
         Competition, on page 106, that you compete with companies that have
entered the MQC
         testing market with alternative automated solutions, such as
Interscience. Please revise to
         reconcile or clarify these disclosures.
Our market, page 6

4.       Please expand your disclosure to describe how you developed the
estimates of your total
         addressable market, or TAM, where discussed in both the Summary and
Business sections
         of the prospectus.
Risk Factors, page 14

5.       We note your disclosure on page 16 in the risk factor, "Our revenue
from customers is
         highly concentrated," that 45.8% of our revenue was generated from two
customers and
         46.1% of our revenue was generated from three customers in the years
ended December
         31, 2019 and 2020, respectively. Please expand the Summary and
Business disclosure to
         discuss your dependence on a few major customers. See Item
101(h)(4)(vi) of Regulation
         S-K.
Market and Industry Data, page 53

6.       You state that you have not independently verified market and industry
data from third-
         party sources and that the market definitions employed have not been
verified by any
         independent source. Please note that you are responsible for the
entire contents of the
         registration statement. Please revise your disclosure to remove any
implication that you
         are not responsible for assessing the reasonableness and soundness of
the market and
         industry data and definitions included in your disclosures.
Capitalization, page 56

7.       Please revise the table to include debt as part of your
capitalization.
Critical accounting policies and significant judgments and estimates, page 75

8.       We note from page 66 the description of your consumables and LIMS
connection
         software, especially that the latter is "optional". Referring to the
revenue recognition
         policy on page 76, please clarify herein and in the significant
accounting policy on pages
         F-16-F-17 whether your proprietary consumables and/or LIMS software
can be purchased
         and/or effectively utilized without the Growth Direct System (as
described on page 5).
         Explain how the Growth Direct system can operate as intended without
these products.
         Finally, explain why the purchase of the consumables and/or the
installation of the
         software would not constitute a separate performance obligation if
there is no binding
         agreement or requirement to purchase the consumables and/or the
software and these
         products can be used without each other, if true.
 Robert Spignesi
Rapid Micro Biosystems, Inc.
April 19, 2021
Page 3
Business
License agreement, page 105

9.     Please expand your disclosure regarding the Thermo Fisher license
agreement to disclose
       the fees paid to date under the agreement and the royalty rate you are
obligated to pay,
       within a ten percent range. In addition, we note the license will remain
in effect until the
       last to expire licensed patent right. Please separately disclose the
expiration year of the
       licensed patents in the Intellectual Property section.
Intellectual property, page 105

10.    Please expand your disclosure to address the following:
           disclose the foreign jurisdictions where you have been issued or
granted patents and
           where you have patent applications pending; and
           disaggregate the number of your owned patents by type of patent or
patent family and
           disclose the related expiration dates for each group.
Government Regulation, page 106

11.    We note your disclosure in this section that your Growth Direct platform
is not directly
       subject to regulation by the FDA. Please expand your disclosure to
explain what
       regulations the company adheres to in developing its products, including
the Growth
       Direct platform.
Principal stockholders, page 127

12.    Please identify the natural person(s) with voting and/or dispositive
power over the shares
       owned by Colony Harvest Ltd. and Endeavour Medtech Growth II LP.

       You may contact Jenn Do at 202-551-3743 or Daniel Gordon at 202-551-3486
if you
have questions regarding comments on the financial statements and related
matters. Please
contact David Gessert at 202-551-2326 or Laura Crotty at 202-551-7614 with any
other
questions.



                                                             Sincerely,
FirstName LastNameRobert Spignesi
                                                             Division of
Corporation Finance
Comapany NameRapid Micro Biosystems, Inc.
                                                             Office of Life
Sciences
April 19, 2021 Page 3
cc:       Wesley C. Holmes
FirstName LastName