Filed by NioCorp Developments Ltd.

pursuant to Rule 425 under the Securities Act of 1933

and deemed filed pursuant to Rule 14a-12

under the Securities Exchange Act of 1934

Subject Company: GX Acquisition Corp. II

Commission File No.: 001-40226

Below is a transcript of an interview by Proactive with Mark A. Smith, CEO and Executive Chairman of NioCorp Developments Ltd. (“NioCorp” or the “Company”), discussing the proposed business combination (the “Transaction”) between NioCorp and GX Acquisition Corp. II (“GXII” or “GX”).

A recording of the interview can be found at the following link: https://www.youtube.com/watch?v=VGPLnPNEoZs.

Participants:

·Mark A. Smith, CEO and Executive Chairman of NioCorp

·Stephen Gunnion, Proactive

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Stephen Gunnion:

Hello, thanks for watching Proactive. NioCorp Developments has announced a tie up with GX Acquisition Corp II to acquire funds for high grade niobium mining in Nebraska. With more, I'm joined by NioCorp CEO and Executive Chairman Mark Smith. Mark, very good to see you again.

Mark Smith:

Great to see you too. Stephen, thanks for your interest.

Stephen Gunnion:

You're welcome. So, Mark, this deal announced last week. Is this essentially a reverse listing into GXII?

Mark Smith:

Absolutely it does provide very quick listing for us on the NASDAQ. So that's extremely positive. Capital markets are outstanding out of New York. So the NASDAQ listing will be a tremendous attribute for us. But it's also a form of finance, financial engineering, so to speak. GX has over $300 million in the trust account. And if we can convince their shareholders that investing in NioCorp is a good idea, which I think we can given our story, we will also receive a tremendous amount of money into our treasury. They will get NioCorp stock.

Stephen Gunnion:

Well, give us give us the story that you're giving to those GXII investors and why they should go ahead with this.

Mark Smith:

I think we only have a few minutes, Steve. So I'll try to do the very short version. But I would love to spend you know two or three hours with you to go through the whole story. But the bottom line is, is that we have a greenfield mine that we want to build and operate in the southeast corner of the state of Nebraska in the United States of America. That greenfields mine is going to have three products for sure. niobium, scandium and titanium. All three of which are critical and strategic minerals, absolutely necessary for the EV revolution, the lightweighting revolution, all the green programs that one can think of, and then we're working on the technical aspects to hopefully include rare earths into our product line as well. We would be producing the magnetic rare earth assuming that technical information provides the guidance that we need to make that ultimate decision. And as you know, EVs are the wave of the future. And everybody in every country is buying EVs at this point in time, we're now up above 5% in terms of total automobile sales, and the automobile industry looks at that as a key point. That's an inflection point

where they are going to start building more and more of these EVs. So we're going to have to have the magnetic rare earth elements to put into the permanent rare earth magnet motors that we need in the EVs. So this is very exciting, really provides a lot of tailwinds for NioCorp, because all of our products will ultimately be critical, strategic, and all part of the green movement going forward, we're really in a great place right now.

Stephen Gunnion:

We've discussed this before Mark, so particularly with legislation in the United States pushing towards electric vehicles. And with the Inflation Reduction Act, this has become a lot more urgent hasn't it?

Mark Smith:

It really has, Steve because you know, the Inflation Reduction Act has requirements. In order for a purchaser of an EV in the United States to receive that EV tax credit of $7,500, you're gonna have to have certain components of that vehicle manufacturer coming from the United States as the primary supplier. Some of those requirements start in 2023. And you know, last time I checked the calendar, that's about two and a half months from now.

Stephen Gunnion:

So as you see it now, the combined business will have net cash of about $285 million, which will be used to advance the Elk Creek and Critical Minerals project. You're also looking at raising additional financing, is that right?

Mark Smith:

That's correct. And we actually have non-binding term sheets that we've signed up with a financial firm out of New York called Yorkville, and that includes two products. One is a convertible debt facility for $16 million. And the other one is what's called a SEPA, a Standby Equity Purchase Agreement, similar to an ATM, if we use, you know, the kind of the SEC language for it, and that's where $65 million is. So we have an additional $81 million available to us through those two financings. And as we're going out and meeting the GX shareholders and talking to them about our project, and why we think they should stay into the NioCorp shareholding position, you know, we'll be meeting with lots of other people as well. And we'll see what the possibilities are for additional fundraising as a result of that.

Stephen Gunnion:

What sort of timing are we looking at for this, Mark, when would you envisage being listed on NASDAQ?

Mark Smith:

You know, it's a great question. The but I think there are two views right now, when you just take a look at the overall average de-SPACing process, that's kind of in the four to six month range. But in our instance, we have a very unique SPAC situation where number one, we're acquiring them. Normally the SPAC goes out and finds somebody to acquire. We're actually acquiring them. And then we'll take over their NASDAQ Listing. But we also have two publicly traded companies in this instance, NioCorp has been publicly traded for a long time. We've been part of the SEC reporting system for over six years. GXII is also a traded company. They've been part of the SEC reporting system for almost two years now. So we have two entities that are well known by the SEC. We don't have the other problem that SPACs have had recently where the publicly traded SPAC is acquiring a privately held company. They have all kinds of problems with the valuations that are being applied to the privately held company. We don't have that problem. Both of our valuations are known every single second of every single trading day. So we can keep things very controlled, very reasonable. And I think, you know, a glass half full person and I think that will get through the SEC process sooner, at least, that's my hope.

Stephen Gunnion:

And of course, you will be maintaining your Toronto Exchange listing at the same time.

Mark Smith:

We will be dual listed, that's right.

Stephen Gunnion:

Well, Mark, I hope you'll keep us posted on developments as they occur. Thank you very much for speaking with us today.

Mark Smith:

It was my pleasure. And we look forward to seeing you again, Steve. Thank you very much.

Stephen Gunnion:

That's Mark Smith, the CEO and Executive Chairman of NioCorp Developments.

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Additional Information about the Proposed Transaction and Where to Find It

In connection with the proposed Transaction, NioCorp intends to file a registration statement on Form S-4 (the “registration statement”) with the U.S. Securities and Exchange Commission (“SEC”), which will include a document that serves as a prospectus and proxy circular of NioCorp and a proxy statement of GXII, referred to as a “joint proxy statement/prospectus.” The definitive joint proxy statement/prospectus will be filed with the SEC as part of the registration statement and, in the case of NioCorp, with the applicable Canadian securities regulatory authorities, and will be sent to all NioCorp shareholders and GXII stockholders as of the applicable record date to be established. Each of NioCorp and GXII may also file other relevant documents regarding the proposed Transaction with the SEC and, in the case of NioCorp, with the applicable Canadian securities regulatory authorities. BEFORE MAKING ANY VOTING OR INVESTMENT DECISION, INVESTORS AND SECURITY HOLDERS OF NIOCORP AND GXII ARE URGED TO READ THE REGISTRATION STATEMENT, THE DEFINITIVE JOINT PROXY STATEMENT/PROSPECTUS AND ALL OTHER RELEVANT DOCUMENTS FILED OR THAT WILL BE FILED WITH THE SEC AND, IN THE CASE OF NIOCORP, WITH THE APPLICABLE CANADIAN SECURITIES REGULATORY AUTHORITIES IN CONNECTION WITH THE PROPOSED TRANSACTION, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THESE DOCUMENTS, CAREFULLY AND IN THEIR ENTIRETY BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION.

Investors and security holders will be able to obtain free copies of the registration statement and the joint proxy statement/prospectus (if and when available) and all other relevant documents that are filed or that will be filed with the SEC by NioCorp or GXII through the website maintained by the SEC at www.sec.gov. Investors and security holders will be able to obtain free copies of the joint proxy statement/prospectus (if and when available) and all other relevant documents that are filed or that will be filed with the applicable Canadian securities regulatory authorities by NioCorp through the website maintained by the Canadian Securities Administrators at www.sedar.com. The documents filed by NioCorp and GXII with the SEC and, in the case of NioCorp, with the applicable Canadian securities regulatory authorities also may be obtained by contacting NioCorp at 7000 South Yosemite, Suite 115, Centennial CO 80112, or by calling (720) 639-4650; or GXII at 1325 Avenue of the Americas, 28th Floor, New York, NY 10019, or by calling (212) 616-3700.

Participants in the Solicitation

NioCorp, GXII and certain of their respective directors, executive officers and other members of management and employees may, under SEC rules, be deemed to be participants in the solicitation of proxies from NioCorp’s shareholders and GXII’s stockholders in connection with the proposed Transaction. Information regarding the executive officers and directors of NioCorp is included in its management information and proxy circular for its 2021 annual general meeting of shareholders filed with the SEC and the applicable Canadian securities regulatory authorities on October 22, 2021. Information regarding the executive officers and directors of GXII is included in its Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 25, 2022. Additional information regarding the persons who may be deemed to be participants in the solicitation, including information regarding their interests in the proposed Transaction, will be contained in the registration statement and the joint proxy statement/prospectus (if and when available). NioCorp’s shareholders and GXII’s stockholders and other interested parties may obtain free copies of these documents free of charge by directing a written request to NioCorp or GXII.

No Offer or Solicitation

This communication and the information contained herein do not constitute (i) (a) a solicitation of a proxy, consent or authorization with respect to any securities or in respect of the proposed Transaction or (b) an offer to sell or the solicitation of an offer to buy any security, commodity or instrument or related derivative, nor shall there be any sale of securities in any jurisdiction in which the offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such jurisdiction or (ii) an offer or commitment to lend, syndicate or arrange a financing, underwrite or purchase or act as an agent or advisor or in any other capacity with respect to any transaction, or commit capital, or to participate in any trading strategies. No offer of securities in the United States or to or for the account or benefit of U.S. persons (as defined in Regulation S under the U.S. Securities Act) shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended (the “Securities Act”), or an exemption therefrom. Investors should consult with their counsel as to the applicable requirements for a purchaser to avail itself of any exemption under the Securities Act. In Canada, no offering of securities shall be made except by means of a prospectus in accordance with the requirements of applicable Canadian securities laws or an exemption therefrom. This communication is not, and under no circumstances is it to be construed as, a prospectus, offering memorandum, an advertisement or a public offering in any province or territory of Canada. In Canada, no prospectus has been filed with any securities commission or similar regulatory authority in respect of any of the securities referred to herein.

Forward-Looking Statements

This communication contains forward-looking statements within the meaning of the United States Private Securities Litigation Reform Act of 1995 and forward-looking information within the meaning of applicable Canadian securities laws. Forward-looking statements may include, but are not limited to, statements about the parties’ ability to close the proposed Transaction, including NioCorp and GXII being able to receive all required regulatory, third-party and shareholder approvals for the proposed Transaction; the anticipated benefits of the proposed Transaction, including the potential amount of cash that may be available to the combined company upon consummation of the proposed Transaction and the use of the net proceeds following the redemptions by GXII public shareholders; NioCorp’s expectation that its common shares will be accepted for listing on the Nasdaq Stock Market following the closing of the proposed Transaction; the execution of definitive agreements relating to the convertible debenture transaction and the stand

by equity purchase facility contemplated by the term sheets with Yorkville Advisors Global, LP (“Yorkville”); the financial and business performance of NioCorp; NioCorp’s anticipated results and developments in the operations of NioCorp in future periods; NioCorp’s planned exploration activities; the adequacy of NioCorp’s financial resources; NioCorp’s ability to secure sufficient project financing to complete construction and commence operation of the Elk Creek Project; NioCorp’s expectation and ability to produce niobium, scandium, and titanium at the Elk Creek Project; the outcome of current recovery process improvement testing, and NioCorp’s expectation that such process improvements could lead to greater efficiencies and cost savings in the Elk Creek Project; the Elk Creek Project’s ability to produce multiple critical metals; the Elk Creek Project’s projected ore production and mining operations over its expected mine life; the completion of the demonstration plant and technical and economic analyses on the potential addition of magnetic rare earth oxides to NioCorp's planned product suite; the exercise of options to purchase additional land parcels; the execution of contracts with engineering, procurement and construction companies; NioCorp’s ongoing evaluation of the impact of inflation, supply chain issues and geopolitical unrest on the Elk Creek Project’s economic model; the impact of health epidemics, including the COVID-19 pandemic, on NioCorp’s business and the actions NioCorp may take in response thereto; and the creation of full time and contract construction jobs over the construction period of the Elk Creek Project. In addition, any statements that refer to projections (including Averaged EBITDA, Averaged EBITDA Margin, and After-Tax Cumulative Net Free Cash Flow), forecasts or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking statements. Forward-looking statements are typically identified by words such as “plan,” “believe,” “expect,” “anticipate,” “intend,” “outlook,” “estimate,” “forecast,” “project,” “continue,” “could,” “may,” “might,” “possible,” “potential,” “predict,” “should,” “would” and other similar words and expressions, but the absence of these words does not mean that a statement is not forward-looking.

The forward-looking statements are based on the current expectations of the management of NioCorp and GXII, as applicable, and are inherently subject to uncertainties and changes in circumstances and their potential effects and speak only as of the date of such statement. There can be no assurance that future developments will be those that have been anticipated. Forward-looking statements reflect material expectations and assumptions, including, without limitation, expectations, and assumptions relating to: the future price of metals; the stability of the financial and capital markets; NioCorp and GXII being able to receive all required regulatory, third-party, and shareholder approvals for the proposed Transaction; the amount of redemptions by GXII public shareholders; the execution of definitive agreements relating to the convertible debenture transaction and the stand by equity purchase facility contemplated by the term sheets with Yorkville; and other current estimates and assumptions regarding the proposed Transaction and its benefits. Such expectations and assumptions are inherently subject to uncertainties and contingencies regarding future events and, as such, are subject to change. Forward-looking statements involve a number of risks, uncertainties or other factors that may cause actual results or performance to be materially different from those expressed or implied by these forward-looking statements. These risks and uncertainties include, but are not limited to, those discussed and identified in public filings made by NioCorp and GXII with the SEC and, in the case of NioCorp, with the applicable Canadian securities regulatory authorities and the following: the amount of any redemptions by existing holders of GXII Class A Shares being greater than expected, which may reduce the cash in trust available to NioCorp upon the consummation of the business combination; the occurrence of any event, change or other circumstances that could give rise to the termination of the Business Combination Agreement and/or payment of the termination fees; the outcome of any legal proceedings that may be instituted against NioCorp or GXII following announcement of the Business Combination Agreement and the transactions contemplated therein; the inability to complete the proposed transactions due to, among other things, the failure to obtain NioCorp

shareholder approval or GXII shareholder approval or the execution of definitive agreements relating to the convertible debenture transaction and the stand by equity purchase facility contemplated by the term sheets with Yorkville; the risk that the announcement and consummation of the proposed transactions disrupts NioCorp’s current plans; the ability to recognize the anticipated benefits of the proposed transactions; unexpected costs related to the proposed transactions; the risks that the consummation of the proposed transactions is substantially delayed or does not occur, including prior to the date on which GXII is required to liquidate under the terms of its charter documents; NioCorp’s ability to operate as a going concern; NioCorp’s requirement of significant additional capital; NioCorp’s limited operating history; NioCorp’s history of losses; cost increases for NioCorp’s exploration and, if warranted, development projects; a disruption in, or failure of, NioCorp’s information technology systems, including those related to cybersecurity; equipment and supply shortages; current and future offtake agreements, joint ventures, and partnerships; NioCorp’s ability to attract qualified management; the effects of the COVID-19 pandemic or other global health crises on NioCorp’s business plans, financial condition and liquidity; estimates of mineral resources and reserves; mineral exploration and production activities; feasibility study results; changes in demand for and price of commodities (such as fuel and electricity) and currencies; changes or disruptions in the securities markets; legislative, political or economic developments; the need to obtain permits and comply with laws and regulations and other regulatory requirements; the possibility that actual results of work may differ from projections/expectations or may not realize the perceived potential of NioCorp’s projects; risks of accidents, equipment breakdowns, and labor disputes or other unanticipated difficulties or interruptions; the possibility of cost overruns or unanticipated expenses in development programs; operating or technical difficulties in connection with exploration, mining, or development activities; the speculative nature of mineral exploration and development, including the risks of diminishing quantities of grades of reserves and resources; claims on the title to NioCorp’s properties; potential future litigation; and NioCorp’s lack of insurance covering all of NioCorp’s operations.

Should one or more of these risks or uncertainties materialize or should any of the assumptions made by the management of NioCorp and GXII prove incorrect, actual results may vary in material respects from those projected in these forward-looking statements.

All subsequent written and oral forward-looking statements concerning the proposed Transaction or other matters addressed herein and attributable to NioCorp, GXII or any person acting on their behalf are expressly qualified in their entirety by the cautionary statements contained or referred to herein. Except to the extent required by applicable law or regulation, NioCorp and GXII undertake no obligation to update these forward-looking statements to reflect events or circumstances after the date hereof to reflect the occurrence of unanticipated events.

Mineral Reserves and Resources

Unless otherwise indicated, information concerning NioCorp’s mining property included in this communication has been prepared in accordance with the requirements of National Instrument 43-101 – Standards of Disclosure for Mineral Projects” (“NI 43-101”) and the Canadian Institute of Mining and Metallurgy (“CIM”) “Definition Standards – For Mineral Resources and Mineral Reserves, May 10, 2014” (the “CIM Definition Standards”). Beginning with NioCorp’s Annual Report on Form 10-K for the fiscal year ended June 30, 2022 (the “NioCorp Form 10-K”), NioCorp’s mining property disclosures included or incorporated by reference in its SEC filings are required to be prepared in accordance with the requirements of subpart 1300 of Regulation S-K (“S-K 1300”). Previously, NioCorp prepared its estimates of mineral resources and mineral reserves following only NI 43-101 and the CIM Definition Standards. On June 28, 2022, NioCorp issued a CIM-compliant NI 43-101 technical report (the “2022 NI 43-101 Elk Creek Technical Report”) for

the Elk Creek Project, which is available through the website maintained by the Canadian Securities Administrators at www.sedar.com. On September 6, 2022, the Company filed a technical report summary for the Elk Creek Project that conforms to S-K 1300 reporting standards (the “S-K 1300 Elk Creek Technical Report Summary”) as Exhibit 96.1 to the NioCorp Form 10-K, which is available through the website maintained by the SEC at www.sec.gov. The 2022 NI 43-101 Elk Creek Technical Report and S-K 1300 Elk Creek Technical Report Summary are based on a feasibility study (the “June 2022 Feasibility Study”) prepared by qualified persons (within the meaning of both NI 43-101 and S-K 1300, as applicable) and are substantively identical to one another except for internal references to the regulations under which the report is made, and certain organizational differences. The requirements and standards under Canadian securities laws, however, differ from those under S-K 1300. The terms “mineral resource,” “indicated mineral resource” and “mineral reserve” included herein are used as defined in accordance with NI 43-101 under the CIM Definition Standards. While the terms are substantially similar to the same terms defined under S-K 1300, there are differences in the definitions. Accordingly, there is no assurance any mineral resource or mineral reserve estimates that the Company may report under NI 43-101 will be the same as the mineral resource or mineral reserve estimates that the Company may report under S-K 1300.

NioCorp discloses estimates of both its mineral resources and mineral reserves. You are cautioned that mineral resources are subject to further exploration and development and are subject to additional risks and no assurance can be given that they will eventually convert to future reserves. Under both regimes, inferred resources, in particular, have a great amount of uncertainty as to their existence and their economic and legal feasibility. Investors are cautioned not to assume that any part or all of the inferred resource exists or is economically or legally mineable. See Item 1A, Risk Factors in the NioCorp Form 10-K. Reference should be made to the full text of the 2022 NI 43-101 Elk Creek Technical Report and the S-K 1300 Elk Creek Technical Report Summary for further information regarding the assumptions, qualifications and procedures relating to the estimates of mineral reserves and mineral resources as defined under NI 43-101 and S-K 1300, respectively.

Qualified Persons

All technical and scientific information included in this communication derived from the June 2022 Feasibility Study respecting NioCorp’s mineral resources has been reviewed and approved by Matthew Batty, P.Geo., Owner, Understood Mineral Resources Ltd., and all such information respecting NioCorp’s mineral reserves has been reviewed and approved by Richard Jundis, P. Eng., Director of Mining, Optimize Group. Each of Mr. Batty and Mr. Jundis and their respective firms are independent consultants who provide consulting services to NioCorp. All other technical and scientific information included in this communication has been reviewed and approved by Scott Honan, M.Sc., SME-RM, NioCorp’s Chief Operating Officer. Each of Messrs. Batty, Jundis, and Honan is a “Qualified Person” as such term is defined in NI 43-101.