# EDGAR Filing Document

**Accession Number:** 0001739410
**File Stem:** 0000950170-23-006125
**Filing Date:** 2023-3
**Character Count:** 34578
**Document Hash:** 786705041c29b2a14b3541b250db993b
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000950170-23-006125.hdr.sgml**: 20230306

**ACCESSION NUMBER**: 0000950170-23-006125

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 16

**CONFORMED PERIOD OF REPORT**: 20230306

**ITEM INFORMATION**: Results of Operations and Financial Condition

**ITEM INFORMATION**: Regulation FD Disclosure

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20230306

**DATE AS OF CHANGE**: 20230306

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Rallybio Corp
- **CENTRAL INDEX KEY:** 0001739410
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **IRS NUMBER:** 851083789
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-40693
- **FILM NUMBER:** 23707663

**BUSINESS ADDRESS:**
- **STREET 1:** 234 CHURCH STREET
- **STREET 2:** SUITE 1020
- **CITY:** NEW HAVEN
- **STATE:** CT
- **ZIP:** 06510
- **BUSINESS PHONE:** 203- 859-3820

**MAIL ADDRESS:**
- **STREET 1:** 234 CHURCH STREET
- **STREET 2:** SUITE 1020
- **CITY:** NEW HAVEN
- **STATE:** CT
- **ZIP:** 06510

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Rallybio Holdings, LLC
- **DATE OF NAME CHANGE:** 20180502

?xml version="1.0" encoding="ASCII"? 8-K

**UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549**

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**FORM** 8-K

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**CURRENT REPORT**

**Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934**

**Date of Report (Date of earliest event reported):** March 6, 2023<br>

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RALLYBIO CORPORATION

**(Exact name of Registrant as Specified in Its Charter)**

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| | | |
|:---|:---|:---|
| Delaware | 001-40693 | 85-1083789 |
| **(State or Other Jurisdiction<br>of Incorporation)** | **(Commission File Number)** | **(IRS Employer<br>Identification No.)** |
|  | 234 Church Street**,** Suite 1020 |  |
|  | New Haven**,** Connecticut | 06510 |
|  | **(Address of Principal Executive Offices)** | **(Zip Code)** |

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**Registrant's Telephone Number, Including Area Code:** 203 859-3820<br>

**(Former Name or Former Address, if Changed Since Last Report)**

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Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

**Securities registered pursuant to Section 12(b) of the Act:**

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| | | |
|:---|:---|:---|
| **<br>Title of each class** | **Trading<br>Symbol(s)** | **<br>Name of each exchange on which registered** |
| Common Stock, par value $0.0001 per share | RLYB | NASDAQ Global Select Market |

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Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company

☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.

☐

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**Item 2.02 Results of Operations and Financial Condition.**

On March 6, 2023, Rallybio Corporation issued a press release announcing its financial results for the quarter and year ended December 31, 2022. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K.

The information contained in Item 2.02 of this Current Report on Form 8-K (including Exhibit 99.1) shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the Exchange Act) or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933 or the Exchange Act, except as expressly set forth by specific reference in such a filing.

**Item 7.01. Regulation FD Disclosure.** 

On March 6, 2023, Rallybio Corporation issued a press release announcing that clinical proof-of-concept has been achieved in a Phase 1b study for RLYB212, an anti-HPA-1a monoclonal antibody for the prevention of Fetal and Neonatal Alloimmune Thrombocytopenia. Results show that one week after a single subcutaneous dose, RLYB212 was able to rapidly and completely eliminate transfused, HPA-1a positive platelets in HPA-1a negative subjects. A copy of the press release is furnished as Exhibit 99.2 to this Current Report on Form 8-K and is incorporated herein by reference.

The information contained in this Item 7.01 of this Current Report on Form 8-K (including Exhibit 99.2) shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the Exchange Act) or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933 or the Exchange Act, except as expressly set forth by specific reference in such a filing.

**Item 9.01 Financial Statements and Exhibits.**

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| | |
|:---|:---|
| (d) Exhibits |  |
| Exhibit No. | Description |
| 99.1 | [<u>Press release issued by the Company on March 6, 2023 regarding financial results for the fiscal quarter and year ended December 31, 2022</u>](rlyb-ex99_1.htm) |
| 99.2 | [<u>Press release issued by the Company on March 6, 2023</u>](rlyb-ex99_2.htm) |
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document) |

---

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**SIGNATURES**

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

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| | | | |
|:---|:---|:---|:---|
|  |  |  | **RALLYBIO CORPORATION** |
| Date: | March 6, 2023 | By:  | /s/ Jonathan Lieber |
|  |  |  | Jonathan Lieber<br>Chief Financial Officer and Treasurer |

---

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## Ex-99

![img96626370_0.jpg](img96626370_0.jpg)

**Rallybio Reports Fourth Quarter and Full Year 2022 Financial Results**

-- Proof-of-Concept Achieved for RLYB212; Showed Rapid and Complete Elimination of Transfused HPA-1a Positive Platelets in HPA-1a Negative Subjects –

-- Phase 1 Multiple Dose Cohort RLYB212 Study Initiated --

-- Phase 1 Multiple Ascending Dose Study of RLYB116 Continues to Progress; Safety, PK and PD Data Expected in 4Q 2023 --

-- $169.0 million cash, cash equivalents and marketable securities as of December 31, 2022; Provides Runway into 1Q 2025--

NEW HAVEN, Conn. March 6, 2023-- Rallybio Corporation (Nasdaq: RLYB), a clinical-stage biotechnology company committed to identifying and accelerating the development of life-transforming therapies for patients with severe and rare diseases, today reported financial results for the fourth quarter and full year ended December 31, 2022 and provided an update on recent program and corporate developments.

"In 2023, we will fortify our position as a leader in the development of transformative medicines for underserved rare diseases," said Martin Mackay, Ph.D., Chief Executive Officer of Rallybio. "Earlier today, we announced proof-of-concept for RLYB212, our product candidate for the prevention of fetal and neonatal alloimmune thrombocytopenia (FNAIT). These data show that RLYB212 was able to markedly accelerate the elimination of transfused HPA-1a positive platelets in HPA-1a negative subjects, supporting our development of RLYB212 as a potential first-in-class medicine to prevent HPA-1a alloimmunization and, ultimately, eliminate FNAIT. We are now enrolling the multiple dose cohort of our Phase 1 trial and look forward to sharing additional data in the fourth quarter of 2023."

Dr. Mackay continued, "In parallel, we are advancing our efforts across complement dysregulation, hematology and metabolic disorders. In the fourth quarter of 2022, we initiated a multiple ascending dose Phase 1 study of RLYB116, our inhibitor of complement component 5 (C5), and we look forward to sharing initial data from this study in the fourth quarter of 2023. In addition, we entered into a collaboration with AbCellera, under which we will co-develop programs for up to five rare disease targets. Following our offering of common stock and pre-funded warrants in November 2022, we believe our capital will enable us to advance our growing portfolio through upcoming milestones, and opportunistically invest in strategic business development transactions that may allow us to broaden our impact and deliver life-transforming therapies to patients globally."

**Recent Business Highlights and Upcoming Milestones:**

**Maternal Fetal Blood Disorders**

Rallybio announced today that proof-of-concept has been achieved in a Phase 1b study for RLYB212, an anti-HPA-1a monoclonal antibody for the prevention of fetal and neonatal alloimmune thrombocytopenia. Results showed that one week after a single subcutaneous dose, RLYB212 was able to rapidly and completely eliminate transfused, HPA-1a positive platelets in HPA-1a negative subjects. RLYB212 was observed to be well-tolerated with no serious adverse events reported.

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The Company believes that the broad range of pharmacokinetic and pharmacodynamic data in the Phase 1b study will allow for substantive modeling to inform dose selection for a future registrational study.

The Company expects to report data from the Phase 1b clinical study of RLYB212 at a scientific conference in 2023.

Rallybio also announced today that testing in the multiple dose cohort of its Phase 1 trial in Europe initiated in the first quarter of 2023. This portion of the Phase 1 study will evaluate safety and pharmacokinetics of RLYB212 based on repeat dosing over 12 weeks in healthy male and female participants. The Company expects results from this cohort of subjects in the fourth quarter of 2023.

The Company continues to advance the FNAIT natural history alloimmunization study. This non-interventional study is designed to inform on the frequency of women at higher risk for FNAIT across a broad population of pregnant women of different racial and ethnic characteristics, and the occurrence of HPA-1a alloimmunization in these women. The Company expects that the data from this study will contribute to a control dataset for a future single armed registration trial for RLYB212.

Given the favorable development profile of RLYB212 as compared to RLYB211 to date, the data generated to date for RLYB212, and the expected manufacturing and supply efficiencies for RLYB212, the Company will not continue development of RLYB211, a plasma-derived polyclonal anti-HPA-1a antibody.

**Complement Dysregulation**

Rallybio initiated dosing in the first multiple ascending dose cohort of a Phase 1 study of RLYB116 in the fourth quarter of 2022. RLYB116 is a novel, potentially long-acting, subcutaneously administered inhibitor of C5 in development for the treatment of patients with complement-related diseases. The single-blind, dose escalation, placebo-controlled study is designed to evaluate the safety, pharmacokinetics, and pharmacodynamics of RLYB116 in healthy participants.

The Company expects initial data from the multiple ascending dose cohort in the fourth quarter of 2023.

Rallybio continues to advance development of RLYB114, formulated for intravitreal injection, for the treatment of ophthalmic disorders.

Rallybio and EyePoint Pharmaceuticals, Inc. announced in February 2023 a research collaboration to explore and assess the viability of utilizing Rallybio's inhibitor of complement component 5 (C5) in EyePoint's Durasert<sup>®</sup>technology for sustained intraocular delivery. The initial focus will be on geographic atrophy, an advanced form of age-related macular degeneration that leads to irreversible vision loss.

**Metabolic Disorders**

Rallybio, together with its partner Exscientia, continues to work toward the selection of a small molecule development candidate to advance into the clinic targeting ENPP1 for the treatment of

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patients with hypophosphatasia (HPP). In vivo efficacy data is expected in the second half of 2023. Following those results, we expect to commence investigational new drug (IND)-enabling studies.

In December 2022, Rallybio announced a strategic alliance with AbCellera to discover, develop, and commercialize novel antibody-based therapeutics for rare diseases. Under the terms of the agreement, AbCellera and Rallybio will co-develop up to five rare disease therapeutic targets, which will be chosen together by both companies. The partnership's first program will focus on addressing the significant unmet therapeutic needs of patients with rare metabolic diseases.

**Hematological Disorders**

Rallybio continues to conduct IND-enabling activities for RLYB331, a preclinical, potentially first-in-class therapeutic monoclonal antibody that inhibits Matriptase-2 (MTP-2), to support the transition of this asset into clinical development.

**Corporate Updates**

In January 2023, Rallybio announced the appointment of Jonathan I. Lieber as Chief Financial Officer (CFO), effective February 1, 2023. Mr. Lieber succeeds Jeffrey Fryer, CPA, Rallybio's Co-Founder and former CFO. The Company announced Mr. Fryer's retirement in June 2022, and following a transition period with Mr. Lieber, Mr. Fryer departed the company on February 15, 2023.

In November 2022, Rallybio consummated a follow-on offering of common stock and pre-funded warrants that raised approximately $55.0 million in gross proceeds.

**Fourth Quarter and Full Year 2021 Financial Results:**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**Research & Development (R&D) Expenses:** R&D expenses were $10.8 million for the fourth quarter of 2022, compared to $6.1 million for the same period in 2021. R&D expenses for the fourth quarter 2022 increased primarily due to an increase in costs to advance RLYB212 and an increase in R&D related headcount costs as compared to the prior year. R&D expenses were $40.7 million for the year ended December 31, 2022 compared to $26.9 million for the year ended December 31, 2021. R&D expenses for the year ended December 31, 2022 increased primarily due to an increase in costs to advance RLYB212, the asset acquisition in-process research and development expense and development expenses of RLYB331 and additional R&D related headcount costs as compared to the prior year including an increase of $2.4 million in share-based compensation expense.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**General & Administrative (G&A) Expenses:** G&A expenses were $6.3 million for the fourth quarter of 2022, compared to $6.2 million for the same period in 2021. G&A expenses were $27.2 million for the year ended December 31, 2022 compared to $18.7 million for the year ended December 31, 2021. The increase in general and administrative expenses for the full year was primarily due to additional G&A related payroll and personnel-related costs, including an increase of $3.5 million in share-based compensation expense, other professional fees, and costs associated with operating as a public company for full fiscal year as compared to 2021.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**Net Loss and Net Loss Per Common Share:** Net loss was $16.2 million for the fourth quarter of 2022, or net loss per common share of $0.46 compared to a net loss

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of $12.4 million, or net loss per common share of $0.42 for the fourth quarter of 2021. Net loss was $66.7 million, or net loss per share of $2.09, for the year ended December 31, 2022 compared to $47.0 million, or net loss per share of $1.84, for the year ended December 31, 2021.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•**Cash Position:** As of December 31, 2022, cash, cash equivalents and marketable securities were $169.0 million.

**About Rallybio**

Rallybio is a clinical-stage biotechnology company committed to identifying and accelerating the development of life-transforming therapies for patients with severe and rare diseases. Since its launch in January 2018, Rallybio has built a portfolio of promising product candidates, which are now in development to address rare diseases in the areas of hematology, immuno-inflammation, maternal fetal health, and metabolic disorders. The Company's mission is being advanced by a team of highly experienced biopharma industry leaders with extensive research, development, and rare disease expertise. Rallybio is headquartered in New Haven, Connecticut, with an additional facility at the University of Connecticut's Technology Incubation Program in Farmington, Connecticut. For more information, please visit **www.rallybio.com**.

**Forward-Looking Statements** <br> This press release contains forward-looking statements that are based on our management's beliefs and assumptions and on currently available information. All statements, other than statements of historical facts contained in this press release are forward-looking statements. In some cases, forward-looking statements can be identified by terms such as "may," "will," "should," "expect," "plan," "anticipate," "could," "intend," "target," "project," "contemplate," "believe," "estimate," "predict," "potential" or "continue" or the negative of these terms or other similar expressions, although not all forward-looking statements contain these words. Forward-looking statements in this press release include, but are not limited to, statements concerning, initiation, substance, design and timing of our planned or ongoing studies for RLYB212 and RLYB116, the timing of the availability of data from such studies, our expectations regarding reporting of data from such studies, and our expectations regarding the usefulness of data from such studies, the potential markets for RLYB212, RLYB114, RLYB116 and RLYB331, our estimates of our capital requirements and the sufficiency thereof, our ability to advance our portfolio, our ability to invest in business development activities, our ability to reach and potential impact on patients globally, our plans for development of RLYB114 for the treatment of ophthalmic disorders, our plans for development activities with our strategic collaboration partners, including Exscientia and Abcellera, the initiation and timing of and plans for our pre-IND enabling studies for our ENPP1 inhibitor, the timing of the availability of data from such studies, the initiation and timing of and plans for our pre-IND enabling studies of RLYB331, and the therapeutic effects of RLYB331. The forward-looking statements in this press release are only predictions and are based largely on management's current expectations and projections about future events and financial trends that management believes may affect Rallybio's business, financial condition and results of operations. These forward-looking statements speak only as of the date of this press release and are subject to a number of known and unknown risks, uncertainties and assumptions, including, but not limited to, our ability to successfully initiate and conduct our planned clinical trials, including the FNAIT natural history study, and the Phase 1 and 1b clinical trials for RLYB212 and the Phase 1 study for RLYB116, and complete such clinical trials and obtain results on our expected timelines, or at all, whether our cash

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resources will be sufficient to fund our operating expenses and capital expenditure requirements and whether we will be successful raising additional capital, our ability to identify new product candidates and successfully acquire such product candidates from third parties, our ability to enter into strategic partnerships or other arrangements, including the development of RLYB114, competition from other biotechnology and pharmaceutical companies, and those risks and uncertainties described in Rallybio's filings with the U.S. Securities and Exchange Commission (SEC), including Rallybio's Quarterly Report on Form 10-Q for the period ended September 30, 2022, and subsequent filings with the SEC. The events and circumstances reflected in our forward-looking statements may not be achieved or occur and actual future results, levels of activity, performance and events and circumstances could differ materially from those projected in the forward-looking statements. Except as required by applicable law, we are not obligated to publicly update or revise any forward-looking statements contained in this press release, whether as a result of any new information, future events, changed circumstances or otherwise.

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**Financial Tables**

**RALLYBIO CORPORATION**

**SELECTED CONDENSED CONSOLIDATED FINANCIAL INFORMATION**

**<br>Condensed Consolidated Statements of Operations and Comprehensive Loss<br>(Unaudited)** 

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| | | | | |
|:---|:---|:---|:---|:---|
|  | **FOR THE THREE MONTHS ENDED<br>DECEMBER 31,** | **FOR THE THREE MONTHS ENDED<br>DECEMBER 31,** | **FOR THE YEAR ENDED<br>DECEMBER 31,** | **FOR THE YEAR ENDED<br>DECEMBER 31,** |
| **(in thousands, except share and per share amounts)** | **2022** | **2021** | **2022** | **2021** |
| Operating expenses: |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Research and development | $10793 | $6094 | $40689 | $26909 |
| &nbsp;&nbsp;&nbsp;&nbsp;General and administrative | 6298 | 6219 | 27195 | 18739 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Total operating expenses | 17091 | 12313 | 67884 | 45648 |
| Loss from operations | (17091) | (12313) | (67884) | (45648) |
| Other income (expenses): |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Interest income | 1071 | 12 | 1963 | 54 |
| &nbsp;&nbsp;&nbsp;&nbsp;Interest expense |  |  |  | (10) |
| &nbsp;&nbsp;&nbsp;&nbsp;Other income | 31 | 109 | 342 | 96 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Total other income, net | 1102 | 121 | 2305 | 140 |
| Loss from continuing operations | (15989) | (12192) | (65579) | (45508) |
| Loss on investment in joint venture | 214 | 223 | 1075 | 1505 |
| Net loss | $(16203) | $(12415) | $(66654) | $(47013) |
| Net loss per common share, basic and diluted | $(0.46) | $(0.42) | $(2.09) | $(1.84) |
| Weighted-average common shares outstanding, basic and diluted | 35516630 | 29789974 | 31821311 | 25519114 |
| Other comprehensive loss (income): |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Net unrealized loss (income) on marketable securities | (220) |  | 214 |  |
| Other comprehensive (loss) income | 220 |  | (214) |  |
| Comprehensive loss | $(15983) | $(12415) | $(66868) | $(47013) |

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**Condensed Consolidated Balance Sheets<br>(Unaudited)** 

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| | | |
|:---|:---|:---|
| **(in thousands)** | **DECEMBER 31,<br>2022** | **DECEMBER 31,<br>2021** |
| Cash, cash equivalents and marketable securities | $168994 | $175334 |
| Total assets | 180435 | 182185 |
| Total liabilities | 11118 | 6583 |
| Total stockholders' equity | 169317 | 175602 |

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**Investor Contacts**

Ami Bavishi

Head of Investor Relations and Corporate Communications

(475) 47-RALLY (Ext. 282)

abavishi@rallybio.com

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Hannah Deresiewicz

Stern Investor Relations, Inc.

212-362-1200

hannah.deresiewicz@sternir.com

**Media Contact**<br>Tara DiMilia<br>908-369-7168<br>Tara.dimilia@tmstrat.com

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## Ex-99

![img97549891_0.jpg](img97549891_0.jpg)

**Rallybio Announces Proof-of-Concept Achieved for RLYB212, a Novel Monoclonal anti-HPA-1a Antibody to Prevent Fetal and Neonatal Alloimmune Thrombocytopenia**

-- RLYB212 Showed Rapid Elimination of Transfused, HPA-1a Positive Platelets in HPA-1a Negative Subjects --

-- Clinical Findings and Safety Profile Consistent with Previously Reported Data; Continue to Support the Potential for RLYB212 as a Prophylactic Treatment for FNAIT --

-- Company Expects to Present Results at a Scientific Conference in 2023 --

NEW HAVEN, Conn. March 6, 2022—Rallybio Corporation (Nasdaq: RLYB) today announced that clinical proof-of-concept has been achieved in a Phase 1b study for RLYB212, an anti-HPA-1a monoclonal antibody for the prevention of fetal and neonatal alloimmune thrombocytopenia (FNAIT). Results show that one week after a single subcutaneous dose, RLYB212 was able to rapidly and completely eliminate transfused, HPA-1a positive platelets in HPA-1a negative subjects.

Additional findings from the study show:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•The reduction in mean platelet elimination half-life was greater than 90% in both RLYB212 dose groups compared to placebo and was dose related.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•The broad range of pharmacokinetic and pharmacodynamic data allows substantive modeling to inform dose selection for a future registrational study.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;•RLYB212 was observed to be well-tolerated with no serious adverse events reported.

The Company expects to report data from the Phase 1b clinical study of RLYB212 at a scientific conference in 2023.

"Our FNAIT development program has consistently demonstrated the effectiveness of anti-HPA-1a antibodies to rapidly eliminate HPA-1a positive platelets from the circulation of HPA-1a negative subjects," commented Róisín Armstrong, Ph.D., Rallybio's RLYB212 Program Lead. "We've also established in published nonclinical studies the association between rapid platelet elimination and prevention of HPA-1a alloimmunization, which can lead to negative and potentially life-threatening outcomes in FNAIT. Collectively, these data reinforce our belief on the potential for an anti-HPA-1a antibody to be a viable approach for preventing FNAIT and we look forward to continued advancement of the RLYB212 development program."

Rallybio also announced today that testing in the multi-dose cohort of its single-center Phase 1 trial in Europe began in the first quarter of 2023. This portion of the Phase 1 study will evaluate safety and pharmacokinetics of RLYB212 based on repeat dosing over 12 weeks in healthy male and female participants. The Company expects results from this cohort of subjects in the fourth quarter of 2023.

Martin Mackay, Ph.D., Chief Executive Officer of Rallybio, stated, "We are very pleased with the progress of our RLYB212 program. Throughout the program, we have carefully laid the groundwork to advance a product candidate that we believe can have a significant impact on

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the lives of expectant mothers and neonates. RLYB212 exemplifies Rallybio's enduring commitment to transforming the treatment of rare diseases with little to no therapeutic options."

Given the favorable development profile of RLYB212 to date, the data generated to date for RLYB212, and the expected manufacturing and supply efficiencies for RLYB212, the Company also announced today that RLYB211, a plasma-derived polyclonal anti-HPA-1a antibody, will not be advanced further in clinical development.

**About the RLYB212 Phase 1b Study**

Rallybio's Phase 1b study is a single-blind, placebo-controlled proof-of-concept study designed to establish the ability of subcutaneous RLYB212 to rapidly accelerate the elimination of HPA-1a positive platelets transfused to HPA-1a negative healthy male participants. In this single-center, EU-based study, the elimination of transfused platelets serves as a surrogate for assessing the ability of an anti-HPA-1a antibody to drive rapid elimination of HPA-1a positive fetal platelets from an expectant mother's circulation, thereby potentially preventing HPA-1a maternal alloimmunization and the occurrence of FNAIT in fetuses and newborns. The platelet challenge in this model represents an equivalent fetal maternal hemorrhage of 30 mL, a rare and catastrophic scenario during pregnancy.

In August 2022, the Company amended the Phase 1b protocol to include a higher dose of RLYB212 and further broaden the range of pharmacokinetic and pharmacodynamic data for RLYB212, enabling substantive modeling of the concentration-effect relationship that can inform dosing for a future registrational study.

The Phase 1b study has been conducted at the Clinical Research department of the Fraunhofer Institute for Translational Medicine and Pharmacology ITMP, in Frankfurt/Main, Germany, in collaboration with the Institute of Transfusion Medicine and Immunohaematology, German Red Cross (Deutsches Rotes Kreuz) Blood Transfusion Service Baden-Württemberg-Hessen gGmbH in Frankfurt/Main, Germany.

**About FNAIT**

Fetal and Neonatal Alloimmune Thrombocytopenia (FNAIT) is a potentially life-threatening rare disease that can cause uncontrolled bleeding in fetuses and newborns. FNAIT can arise during pregnancy due to an immune incompatibility between an expectant mother and her fetus in a specific platelet antigen called human platelet antigen 1, or HPA-1.

There are two predominant forms of HPA-1, known as HPA-1a and HPA-1b, which are expressed on the surface of platelets. Individuals who are homozygous for HPA-1b, meaning that they have two copies of the HPA-1b allele and no copies of the HPA-1a allele, are also known as HPA-1a negative. Upon exposure to the HPA-1a antigen, these individuals can develop antibodies to that antigen in a process known as alloimmunization. In expectant mothers, alloimmunization can occur upon mixing of fetal blood with maternal blood. When alloimmunization occurs in an expectant mother, the anti-HPA-1a antibodies that develop in the mother can cross the placenta and destroy platelets in the fetus. The destruction of platelets in

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the fetus can result in severely low platelet counts, or thrombocytopenia, and potentially lead to devastating consequences including miscarriage, stillbirth, death of the newborn, or severe lifelong neurological disability in those babies who survive. There is currently no approved therapy for the prevention or prenatal treatment of FNAIT.

**About Rallybio**

Rallybio is a clinical-stage biotechnology company committed to identifying and accelerating the development of life-transforming therapies for patients with severe and rare diseases. Since its launch in January 2018, Rallybio has built a portfolio of promising product candidates, which are now in development to address rare diseases in the areas of hematology, immuno-inflammation, maternal fetal health, and metabolic disorders. The Company's mission is being advanced by a team of highly experienced biopharma industry leaders with extensive research, development, and rare disease expertise. Rallybio is headquartered in New Haven, Connecticut, with an additional facility at the University of Connecticut's Technology Incubation Program in Farmington, Connecticut. For more information, please visit **www.rallybio.com**.

**Forward-Looking Statements** 

This press release contains forward-looking statements that are based on our management's beliefs and assumptions and on currently available information. In some cases, forward-looking statements can be identified by terms such as "may," "will," "should," "expect," "plan," "anticipate," "could," "intend," "target," "project," "contemplate," "believe," "estimate," "predict," "potential" or "continue" or the negative of these terms or other similar expressions, although not all forward-looking statements contain these words. Forward-looking statements in this press release include, but are not limited to, statements concerning substance, design and timing of our planned or ongoing studies for RLYB212, the timing of the availability of data from such studies, our expectations regarding reporting of data from such studies, our expectations regarding the usefulness such data, the success of modeling to inform dosing for a future registrational study, our ability to advance RLYB212 into future clinical studies, and the likelihood that Rallybio will be successful in developing RLYB212 as an approach to prevent FNAIT. The forward-looking statements in this press release are only predictions and are based largely on management's current expectations and projections about future events and financial trends that management believes may affect Rallybio's business, financial condition and results of operations. These forward-looking statements speak only as of the date of this press release and are subject to a number of known and unknown risks, uncertainties and assumptions, including, but not limited to, our ability to successfully initiate and conduct our planned clinical trials, including the FNAIT natural history study, and the Phase 1 and 1b clinical trials for RLYB212 and the Phase 1 study for RLYB116, and complete such clinical trials and obtain results on our expected timelines, or at all, whether our cash resources will be sufficient to fund our operating expenses and capital expenditure requirements and whether we will be successful raising additional capital, our ability to identify new product candidates and successfully acquire such product candidates from third parties, our ability to integrate RLYB331 into our pipeline, competition from other biotechnology and pharmaceutical companies, and those risks and uncertainties described in Rallybio's filings with the U.S. Securities and Exchange Commission (SEC), including Rallybio's Annual Report on Form 10-Q for the period ended September 30, 2022, and subsequent filings with the SEC. The events and circumstances reflected in our forward-looking statements may not be achieved or occur and actual future results, levels of activity, performance and events and circumstances could differ materially from those projected in the forward-looking statements. Except as required by applicable law, we are not obligated to

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publicly update or revise any forward-looking statements contained in this press release, whether as a result of any new information, future events, changed circumstances or otherwise.

**Investor Contacts**

Ami Bavishi

Head of Investor Relations and Corporate Communications

(475) 47-RALLY (Ext. 282)

abavishi@rallybio.com

Hannah Deresiewicz

Stern Investor Relations, Inc.

(212) 362-1200

hannah.deresiewicz@sternir.com

**Media Contact**<br>Tara DiMilia<br>(908) 369-7168<br>Tara.dimilia@tmstrat.com

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