WARNING LETTER
Longhorn Vaccines and Diagnostics LLC
MARCS-CMS 721702 —
February 26, 2026
Delivery Method:
VIA Electronic Mail
Product:
Medical Devices
Recipient:
Recipient Name
Jeffrey D. Fischer
Recipient Title
President
Longhorn Vaccines and Diagnostics LLC
7272 Wisconsin Avenue, Ste 900
Bethesda
,
MD
20814
United States
jeff@lhnvd.com
Issuing Office:
Center for Devices and Radiological Health
United States
WARNING LETTER
CMS # 721702
February 26, 2026
Dear Mr. Jeffrey D. Fischer:
During an inspection of your firm located in Bethesda, MD from October 20, 2025 through October 30, 2025, investigators from the United States Food and Drug Administration (FDA) determined that your firm is a specification developer of the PrimeStore® MTM (Molecular Transport Medium) device intended for the stabilization, transportation, and inactivation of infectious unprocessed nasal washes suspected of containing Influenza A virus RNA as well as unprocessed sputum samples suspected of containing
Mycobacterium tuberculosis
DNA from human samples. Under section 201(h) of the Federal Food, Drug, and Cosmetic Act (the Act), 21 U.S.C. § 321(h), these products are devices because they are intended for use in the diagnosis of disease or other conditions or in the cure, mitigation, treatment, or prevention of disease, or to affect the structure or any function of the body.
Quality System Regulation Violations
This inspection revealed that these devices are adulterated within the meaning of section 501(h) of the Act, 21 U.S.C. § 351(h), in that the methods used in, or the facilities or controls used for, their manufacture, packing, storage, or installation are not in conformity with the current good manufacturing practice requirements of the Quality System regulation found at Title 21,
Code of Federal Regulations
(CFR), Part 820. These violations include, but are not limited to, the following:
Failure to maintain complaint files and establish and maintain procedures for receiving,reviewing, and evaluating complaints by a formally designated unit to ensure that allcomplaints are processed in a uniform and timely manner; oral complaints are documentedupon receipt; and complaints are evaluated to determine whether the complaint represents anevent which is required to be reported to FDA under part 803 of this chapter, Medical DeviceReporting, as required by 21 CFR 820.198(a) and 21 CFR 820.198(a)(1) through820.198(a)(3).
Specifically:
A. Complaints files are not adequately maintained, as required by 21 CFR 820.198(a). For example, alleged deficiencies of your PrimeStore® MTM devices received via thirteen (13) emails between 2020 and 2022 were not documented in controlled records.
B. Your firm did not have a procedure for complaint handling (QSP-COM-001; Rev. 1.0; Effective: 10/27/25), until during the inspection. This procedure lacks requirements for:
1) Uniform and timely processing of complaints, as required by 21 CFR 820.198(a)(1);
2) Documentation of oral complaints upon receipt, as required by 21 CFR 820.198(a)(2); and
3) Evaluation of complaints to determine whether the complaint represents an event which is required to be reported to FDA under 21 CFR 803 (Medical Device Reporting), as required by 21 CFR 820.198(a)(3). For example, your firm failed to evaluate complaints for medical device reportability received for your PrimeStore® MTM devices regarding leakage of “
(b)(4)
” between 2020 and 2022; two (2) incidents of ingestion in 2022; two (2) incidents of skin exposure in 2021; and FDA notification of cyanide release in 2020 due to usage on incompatible systems consisting of a bleach step (RES 86189).
2. Failure to review and evaluate all complaints to determine whether an investigation is necessary. When no investigation is made, the manufacturer shall maintain a record that includes the reason no investigation was made and the name of the individual responsible for the decision not to investigate, as required by 21 CFR 820.198(b).
For example, your firm did not review and evaluate whether the two (2) complaints of ingestion in 2022 and two (2) complaints of skin exposure in 2021 required investigations or document reasons for why no investigations were necessary.
3. Failure to investigate any complaint involving the possible failure of a device, labeling or packaging to meet any of its specifications, unless such investigation has already been performed for a similar complaint and another investigation is not necessary, as required by 21 CFR 820.198(c).
Specifically, your firm does not have any documented investigations for the following complaints which involve the possible failure of your PrimeStore® MTM device, labeling, or packaging to meet any of its specifications:
Leakage of “
(b)(4)
” between 2020 and 2022;
Release of cyanide after usage of device on incompatible systems (RES 86189)
4. Failure to establish and maintain procedures for implementing corrective and preventive action, including requirements for analyzing processes, work operations, concessions, quality audit reports, quality records, service records, complaints, returned product, and other sources of quality data to identify existing and potential causes of nonconforming product, or other quality problems using appropriate statistical methodology; investigating the cause of nonconformities relating to product, processes, and the quality system; identifying the action(s) needed to correct and prevent recurrence of nonconforming product and other quality problems; and verifying or validating the corrective and preventive action to ensure that such action is effective and does not adversely affect the finished device, as required by 21 CFR 820.100(a) and 21 CFR 820.100(a)(1) through 820.100(a)(4).
Specifically:
A. Your firm did not have a procedure for implementing corrective and preventive action (CAPA) (QSP-CAPA-001; Rev. 1.0; Effective: 10/27/25), until during this inspection, as required by 21 CFR 820.100(a).
B. Your firm failed to analyze your processes, work operations, complaints, and other sources of quality data to identify existing and potential causes of nonconforming product, or other quality problems, as required by 21 CFR 820.100(a)(1).
C. Your firm failed to investigate the cause and identify actions needed to prevent recurrence along with the verification or validation of the effectiveness of such actions, as required by 21 CFR 820.100(a)(2) through 21 CFR 820.100(a)(4), for the following known, systemic issues:
Field correction RES 86189 initiated on June 3, 2020 urging users to apply labels to the
(b)(4)
PrimeStore® MTM devices which had been distributed without a label and avoid contact with bleach to prevent the release of cyanide gas.
Complaints received for leakage of “
(b)(4)
” between 2020 and 2022.
5. Failure to establish and maintain procedures to control the design of the device in order to ensure that specified design requirements are met to demonstrate that the design was developed in accordance with the design control requirements, as required by 21 CFR 820.30(a) through 820.30(j).
Specifically:
A. Your firm did not have procedures to control the design of your PrimeStore® MTM devices (“PrimeStore® MTM – Design Control Document” created October 18, 2025), until during this inspection, as required by 21 CFR 820.30(a).
B. Your firm did not have a design and development plan in place for your PrimeStore® MTM devices (“Design and Development***” section of “PrimeStore® MTM – Design History File (DHF)” [Rev. 1.0; Effective: 10/21/25]), until during this inspection, as required by 21 CFR 820.30(b). Although the “Design and Development Plan” section of this document contains a historical summary of product development, it fails to define responsibility for implementation and identify and describe the interfaces with different groups or activities that provide, or result in, input to the design and development process.
C. Your firm did not have a design input procedure (“Design Inputs***” section of “PrimeStore® MTM – Design Control Document” created October 18, 2025 which was superseded by “Design Input Procedure***” [SOP-DV-004; Rev. 1.0; Effective: 10/27/25]), until during this inspection, as required by 21 CFR 820.30(c). Although the design input section of the “PrimeStore® MTM – Design Control Document” states “***
(b)(4)
***,” it fails to include a mechanism for addressing incomplete, ambiguous, or conflicting requirements.
For example, the following design inputs, created as a part of the “PrimeStore® MTM – Design History File (DHF)” (Rev. 1.0; Effective: 10/21/25) at the time the “PrimeStore® MTM – Design Control Document” procedure was in effect, are ambiguous in that they lack or fail to make reference to clearly defined requirements:
(b)(4)
(b)(4)
(b)(4)
(b)(4)
D. Your firm did not have a design output procedure (“Design Outputs” section of “PrimeStore® MTM – Design Control Document” created on October 18, 2025 which was superseded by “Design Output Procedure***” [SOP-DV-005; Rev. 1.0; Effective: 10/27/25]), until during this inspection, as required by 21 CFR 820.30(d). Although the design output section of the “PrimeStore® MTM – Design Control Document” states “***
(b)(4)
***,” it fails to require that acceptance criteria be included or referenced and that those design outputs that are essential for the proper functioning of the device are identified.
For example, the following design outputs, created as a part of the “PrimeStore® MTM – Design History File (DHF)” (Rev. 1.0; Effective: 10/21/25) at the time the “PrimeStore® MTM – Design Control Document” procedure was in effect, fail to contain or make reference to acceptance criteria or identify outputs that are essential for proper functioning of your PrimeStore® MTM devices:
The “Tube system” design output only states “
(b)(4)
” with no further references to output documentation.
The “Label set” design output only states “
(b)(4)
” with no further references to output documentation.
The “Manufacturing documents” design output only states “
(b)(4)
” with no further references to output documentation.
The “Packaging” design output only states “
(b)(4)
” with no further references to output documentation.
E. Your firm did not have a design review procedure (“Design Reviews” section of “PrimeStore® MTM – Design Control Document” created on October 18, 2025 which was superseded by “Design Review Procedure***” [SOP-DV-006; Rev. 1.0; Effective: 10/27/25]), until during this inspection, as required by 21 CFR 820.30(e).
F. Your firm did not have a design verification procedure (“Design Verification***” section of “PrimeStore® MTM – Design Control Document” created on October 18, 2025 which was superseded by “Design Verification Procedure ***” [SOP-DV-007; Rev. 1.0; Effective: 10/27/25]), until during this inspection, as required by 21 CFR 820.30(f).
G. Your firm did not have a design validation procedure (“Design Validation***” section of “PrimeStore® MTM – Design Control Document” created October 18, 2025 which was superseded by “Design Validation Procedure***” [SOP-DV-008; Rev. 1.0; Effective: 10/27/25]), until during this inspection, as required by 21 CFR 820.30(g).
H. Your firm did not have a design transfer procedure (“Design Transfer to Production” section of “PrimeStore® MTM – Design Control Document” created on October 18, 2025 which was superseded by “Design Transfer Procedure***” [SOP-DV-009; Rev. 1.0; Effective: 10/27/25]), until during this inspection, as required by 21 CFR 820.30(h).
I. Your firm did not have a design change procedure (“Change Control***” section of “PrimeStore® MTM – Design Control Document” created October 18, 2025 which was superseded by “Design Change Control Procedure***” [SOP-CC-001; Rev. 1.0; Effective: 10/27/25]), until during this inspection, as required by 21 CFR 820.30(i). Although the “Change Control” section of the “PrimeStore® MTM – Design Control Document” requires “***
(b)(4)
***” and “***
(b)(4)
***,” there is no requirement for validation or where appropriate verification, review, and approval of design changes before their implementation.
For example, your firm was unable to provide validation or verification (where appropriate), evidence of review and approval, and assessment for the need of a new premarket authorization submission for the following design changes of your PrimeStore® MTM devices prior to implementation:
Additional tube sizes and fill volume (2mL tube with a 1mL fill volume; 5mL tube with a 1.5mL fill volume; 12mL tube with a 2mL fill volume; and 12mL tube with a 3mL fill volume)
Change in shelf life prior to use from 24 months to 30 months
Changes in the tube
J. Your firm failed to define and document a design history file (DHF) (“PrimeStore® MTM – Design History File (DHF)” (Rev. 1.0; Effective: 10/21/25) and “DHF – History” dated 10/23/25) for your PrimeStore® MTM device, until during this inspection, as required by 21 CFR 820.30(j).
6. Failure to establish and maintain procedures to control product that does not conform to specified requirements, including the identification, documentation, evaluation, segregation, and disposition of nonconforming product. The evaluation of nonconformance shall include a determination of the need for an investigation and notification of the persons or organizations responsible for the nonconformance. The evaluation and any investigation shall be documented, as required by 21 CFR 820.90(a).
Specifically, your firm did not have a procedure to control product that does not conform to specified requirements (QSP-NC-001; Rev. 1; Effective: 10/27/25), until during this inspection. Additionally, your firm failed to identify, document, and evaluate the nonconformances noted in the email dated
(b)(4)
and
(b)(4)
from your contract manufacturers regarding
(b)(4)
underfilled (Lot #
(b)(4)
) and an unknown quantity of discolored (Lot #
(b)(4)
) PrimeStore® MTM devices, respectively, to determine the need for an investigation. In addition, your firm did not evaluate the need for investigations for the nonconformances associated with 2 leaky caps, 43 specks, and 21 floaters (misc.) of PrimeStore® MTM devices (Lot #
(b)(4)
) which were reworked between
(b)(4)
and
(b)(4)
.
7. Failure to establish and maintain procedures for rework, to include retesting and reevaluation of the nonconforming product after rework, to ensure that the product meets its current approved specifications and documentation of rework and reevaluation activities, including determination of any adverse effect from the rework upon the product, in the device history record (DHR), as required by 21 CFR 820.90(b)(2).
Specifically, your firm did not have a procedure for rework (QSP-RWK-001; Rev. 1; Effective: 10/27/25), until during this inspection. For example, your firm failed to conduct retesting and reevaluation of the reworks conducted between July 15, 2025 and July 16, 2025 for nonconformances associated with 2 leaky caps, 43 specks, and 21 floaters (or misc.) for your PrimeStore® MTM devices (Lot #
(b)(4)
), to ensure that the product meets its current approved specifications, including a determination of any adverse effect from these reworks.
8. Failure to establish and maintain procedures to ensure that all purchased or otherwise received product and services conform to specified requirements, as required by 21 CFR 820.50.
Specifically, your firm did not have a procedure to ensure that all suppliers conform to specified requirements (QSP-SUP-001; Rev. 1.0; Effective: 10/27/25), until during this inspection. Additionally:
A. Your firm does not establish and maintain requirements, including quality requirements, that must be met by your suppliers, as required by 21 CFR 820.50(a). For example:
1) Your firm does not have documented evaluations that confirm the ability of
(b)(4)
out of
(b)(4)
of your suppliers to meet requirements, including quality requirements, as required by 21 CFR 820.50(a)(1). This includes suppliers of the bulk liquid media and plastic components as well as finished device contract manufacturers of your PrimeStore® MTM devices.
2) Your firm does not define the type as well as extent of controls to be exercised over your suppliers based on the results of supplier evaluations, as required by 21 CFR 820.50(a)(2).
3) Your firm did not have records of acceptable suppliers (“Longhorn Supplier List” dated 10/28/25), until during this inspection, as required by 21 CFR 820.50(a)(3).
B. Your firm does not have a purchasing agreement in place for
(b)(4)
out of
(b)(4)
of the finished device contract manufacturers of your PrimeStore® MTM devices which involves an agreement to notify you of changes so that you may determine whether the changes affect the quality of your finished device, as required by 21 CFR 820.50(b).
9. Failure of management with executive responsibility to review the suitability and effectiveness of the quality system at defined intervals and with sufficient frequency according to established procedures to ensure that the quality system satisfies the requirements of this part and the manufacturer's established quality policy and objectives, as required by 21 CFR 820.20(c).
Specifically, your firm did not have a procedure which requires that the management with executive responsibility review the suitability and effectiveness of the quality system at defined intervals and with sufficient frequency to ensure that your quality system satisfies the requirement of the regulation and your quality policy and objectives (QP-MR-001; Rev. 1.0; Effective: 10/27/25), until during this inspection. For example, the management review records retrospectively created for 2022, 2023, and 2024 from emails and memory during the inspection were inadequate because they were non-contemporaneous and based on data from incomplete quality metrics (e.g., nonconforming products, CAPAs, supplier and purchasing controls, etc.).
10. Failure to establish procedures for quality audits and conduct such audits to assure that the quality system is in compliance with the established quality system requirements and to determine the effectiveness of the quality system, as required by 21 CFR 820.22.
Specifically, your firm does not have a quality audit procedure and has not conducted quality audits to assure that your quality system is in compliance with established quality system requirements and to determine the effectiveness of your quality system.
On February 2, 2024, the FDA issued a
final rule
amending the device current good manufacturing practice (CGMP) requirements of the Quality System (QS) Regulation under 21 CFR 820 to align more closely with the international consensus standard for Quality Management Systems for medical devices used by many other regulatory authorities around the world. The revised part 820, referred to as the Quality Management System Regulation (QMSR), became effective on February 2, 2026. Your most recent inspection from October 20, 2025 through October 30, 2025 was conducted pursuant to the QS Regulation, which was in effect at the time of the inspection. However, any corrective actions you propose or implement must be pursuant to the QMSR requirements in effect as of February 2, 2026. For more information on the QMSR please refer to our frequently asked questions webpage: https://www.fda.gov/medical-devices/quality-system-qs-regulationmedical-device-current-good-manufacturing-practices-cgmp/quality-management-system-regulation-final-rule-amending-quality-system-regulation-frequently-asked.
Medical Device Reporting (MDR) Violations
Our inspection also revealed that your firm’s PrimeStore® MTM devices are misbranded under section 502(t)(2) of the Act, 21 U.S.C. § 352(t)(2), in that your firm failed or refused to furnish material or information respecting the device that is required by or under section 519 of the Act, 21 U.S.C. § 360i, and 21 CFR Part 803 - Medical Device Reporting. Significant violations include, but are not limited to, the following:
Failure to develop, maintain, and implement written MDR procedures as required by 21 CFR 803.17.
Unapproved Device Violations
Our inspection also revealed that the PrimeStore® MTM device is adulterated under section 501(f)(1)(B) of the Act, 21 U.S.C. § 351(f)(1)(B), because your firm does not have an approved application for premarket approval (PMA) in effect pursuant to section 515(a) of the Act, 21 U.S.C. § 360e(a), or an approved application for an investigational device exemption under section 520(g) of the Act, 21 U.S.C. § 360j(g). The device is also misbranded under section 502(o) the Act, 21 U.S.C. § 352(o), because your firm did not notify the agency of its intent to introduce the device into commercial distribution, as required by section 510(k) of the Act, 21 U.S.C. § 360(k) and 21 CFR 807.81(a)(3)(ii). For a device requiring premarket approval, the notification required by section 510(k) is deemed satisfied when a PMA is pending before the agency. [21 CFR 807.81(b)] The kind of information that your firm needs to submit in order to obtain approval or clearance for the device is described on the Internet at http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/HowtoMarketYourDevice/default.htm. The FDA will evaluate the information that your firm submits and decide whether the product may be legally marketed.
The PrimeStore® MTM was granted marketing authorization following FDA’s review of your firm’s De Novo request under
DEN170029
with the following indications for use:
PrimeStore MTM is intended for the stabilization, transportation and inactivation of infectious unprocessed nasal washes suspected of containing Influenza A virus RNA. PrimeStore MTM is also intended for the stabilization, transportation and inactivation of infectious unprocessed sputum samples suspected of containing Mycobacterium tuberculosis DNA from human samples.
However, your website contains statements and information demonstrating that the PrimeStore MTM is intended for the stabilization and inactivation of numerous additional microorganisms, for the use of numerous additional specimen types and to improve sensitivity in low copy samples outside of the authorized indications. Your website and product brochure also show an intent to market the device for the detection of antimicrobial resistance (AMR) genes. These statements and representations constitute major changes or modifications to the device’s intended use, for which your firm lacks clearance or approval. Examples from your firm’s website include:
1. A list of additional organisms for which your device is intended for stabilization and inactivation, including Crimean-Congo hemorrhagic fever virus, Eastern equine encephalitis virus, Ebola virus, Mpox, as well as many other organisms. (https://www.lhnvd.com/primestore-mtm and https://www.lhnvd.com/product-development))
2. A statement, “PrimeStore MTM was optimized (and patented) to provide consistent results from simple samples like nasal swabs to the most challenging samples like tissue and stool.” (https://www.lhnvd.com/primestore-mtm)
3. A statement, “The USDA recently expanded its use of PrimeStore MTM beyond SARS-CoV-2 and African Swine Fever to facilitate the tracking and surveillance of the avian influenza strain that is infecting wild bird populations and US poultry flocks.” (https://www.lhnvd.com/product-development)
Examples from your firm’s product brochure for the PrimeStore MTM include:
1. A statement “one device for multiple sample types” which lists 14 different sample types including cervical/vaginal, fecal/stool, urine, blood/plasma/serum, tissue, and genital skin.
2. A statement that the PrimeStore MTM can be used to detect “Viruses,” “Parasites,”“Bacteria,” and “Fungi” and to detect “AMR Genes.”
3. A statement, “The device can be used for molecular testing and sequencing of blood,plasma, respiratory samples, urine, tissues and stool in human, animal, avian, plant andenvironmental forensics.” (https://www.lhnvd.com/product-development)
These major changes and/or modifications to the intended use of your device could significantly affect the safety and effectiveness of your device as they suggest that your device can stabilize, transport, and inactivate these new sample types and targets not previously reviewed in your De Novo request. Failure to stabilize a specimen and/or failure to inactivate a specimen can result in inaccurate test results as well as in risks to the user handling clinical specimens without appropriate precautions for the specific pathogen.
The performance data provided in your De Novo request indicates the performance of the previously cleared device to inactivate and stabilize nasal washes containing Influenza A virus RNA or unprocessed sputum samples suspected of containing Mycobacterium tuberculosis DNA. However, it does not demonstrate your device’s ability to inactivate and stabilize other infectious agents or to be effective to inactivate or stabilize any infectious agent in sample types not addressed in the De Novo. FDA is not aware of any data demonstrating the safety and effectiveness of your device when intended for use with such infectious diseases and sample types. If you have data demonstrating these performance characteristics, please provide that information to the agency in a new premarket submission.
Your firm should take prompt action to address any violations identified in this letter. Failure to adequately address this matter may result in regulatory action being initiated by the FDA without further notice. These actions include, but are not limited to, seizure, injunction, and civil money penalties.
Other federal agencies may take your compliance with the Act and its implementing regulations into account when considering the award of federal contracts. Additionally, should FDA determine that you have QS regulation violations that are reasonably related to premarket approval applications for Class III devices, such devices will not be approved until the violations have been addressed. Should FDA determine that your devices or facilities do not meet the requirements of the Act, requests for Certificates to Foreign Governments (CFG) may not be granted.
Please notify this office in writing within fifteen business days from the date you receive this letter of the specific steps your firm has taken to address the noted violations, as well as an explanation of how your firm plans to prevent these violations, or similar violations, from occurring again. Include documentation of the corrections and/or corrective actions (which must address systemic problems) that your firm has taken. If your firm’s planned corrections and/or corrective actions will occur over time, please include a timetable for implementation of those activities. If corrections and/or corrective actions cannot be completed within fifteen business days, state the reason for the delay and the time within which these activities will be completed. Your firm’s response should be comprehensive and address any violations included in this Warning Letter. If you believe that your products are not in violation of the Act, include your reasoning and any supporting information for our consideration as part of your response.
Your firm’s response should be sent via email to Gina Brackett, Establishment Assessment Team 1 Assistant Director at CDRHEnforcement@fda.hhs.gov. Please include in the subject line, “CMS Case 721702” when replying. If you have any questions about the contents of this letter, please contact: Sargum C. Morgan, Compliance Officer at sargum.morgan@fda.hhs.gov.
Finally, you should know that this letter is not intended to be an all-inclusive list of the violations at your firm’s facility. It is your firm’s responsibility to ensure compliance with applicable laws and regulations administered by FDA. The specific violations noted in this letter and in the Inspectional Observations, FDA 483, issued at the close of the inspection may be symptomatic of serious problems in your firm’s manufacturing and quality management systems. Your firm should investigate and determine the causes of any violations and take prompt actions to address any violations and bring the products into compliance.
Sincerely,
/S/
Barbara A. Marsden
Acting Director
Office of Regulatory Programs
Office of Product Evaluation and Quality
Center for Devices and Radiological Health
Content current as of:
03/24/2026
Regulated Product(s)
Medical Devices