RAPA-501-Allo Therapy of COVID-19-ARDS
RAPA-501-Allo Therapy of COVID-19-ARDS
The first-in-human Phase 1 study component will evaluate two dose levels of RAPA-501-ALLO off
 the shelf cells in patients with COVID-19-related ARDS, with key endpoints of safety,
 biologic and potential disease-modifying effects. The randomized, double-blind,
 placebo-controlled Phase 2b study component will evaluate infusion of RAPA-501 ALLO off the
 shelf cells or a control infusion, with the primary endpoint assessing whether RAPA-501 cells
 reduce 30-day mortality.

 The COVID-19 pandemic is a disaster playing out with progressive morbidity and mortality. As
 of April 6th, 2021, an estimated 132.1 million people have contracted the virus and 2,866,000
 deaths have resulted globally. The United States has the highest totals with an estimated
 30.8 million people diagnosed and 556,000 deaths. In stages 1 and 2 of COVID-19, viral
 propagation within the patient is predominant. As such, therapeutic interventions focus on
 immune molecules (convalescent serum, monoclonal antibodies) and anti-viral medications
 (remdesivir). In marked contrast, the most severe and deadly form of COVID-19, stage 3, is
 driven not by viral propagation, but by an out-of-control immune response (hyperinflammation)
 caused by increases in immune molecules known as cytokines and chemokines. As such,
 therapeutic interventions for stage 3 disease focus on anti-inflammatory medications such as
 anti-cytokine therapy (anti-IL-6 drugs) or corticosteroid therapy. Unfortunately, such
 interventions do not address the full pathogenesis of stage 3 COVID-19, which includes
 hyperinflammation due to "cytokine storm" and "chemokine storm," tissue damage,
 hypercoagulation, and multi-organ failure (including lung, heart, kidney and brain). The
 pulmonary component of stage 3 disease includes acute respiratory distress syndrome (ARDS),
 which is a final-common-pathway of patient death due to a myriad of conditions, including
 pneumonia, sepsis, and trauma. There is a dire need for novel cellular treatments that can
 deliver both a broad-based immune modulation effect and a tissue regenerative effect, such as
 RAPA-501-ALLO off-the-shelf allogeneic hybrid TREG/Th2 Cells.

 Stage 3 COVID-19 carries an estimated 30-day mortality of over 50% in spite of ICU
 utilization, mechanical ventilation, and supportive care therapies to manage ARDS and
 multiorgan failure. Narrowly acting targeted anti-inflammatory approaches such as anti-IL-6
 therapeutics have not been particularly effective in stage 3 COVID-19 and the broad
 anti-inflammatory pharmaceutical approach of corticosteroid therapy, has only modestly
 tempered stage 3 disease in some studies. Cell therapy is also being evaluated in stage 3
 COVID-19, in particular, mesenchymal stromal cells (MSC) and now, with the current
 RAPA-501-ALLO protocol, regulatory T (TREG) cells. TREG therapy has a mechanism of action
 that includes a multi-faceted anti-inflammatory effect, which puts TREG therapy at the
 forefront of future curative therapy of a wide range of autoimmune and neurodegenerative
 diseases, plus transplant complications, such as graft-versus-host disease (GVHD) and graft
 rejection. In addition, TREG therapy can provide a tissue regenerative effect, which places
 TREG cell therapy at the lead of novel regenerative medicine efforts to repair a myriad of
 tissue-based diseases, such as diseases of the skin, muscle, lung, liver, intestine, heart
 (myocardial infarction) and brain (stroke). RAPA-501-ALLO off-the-shelf cell therapy offers
 this potential dual threat mechanism of action that incorporates both anti-inflammatory and
 tissue repair effects for effective treatment of COVID-19 and multiple lethal conditions.

 RAPA-501-ALLO cells are generated from healthy volunteers, cryopreserved, banked, and are
 then available for off-the-shelf therapy anytime. During manufacturing, T cells are
 "reprogrammed" ex vivo using a novel, patented 7-day two-step process that involves T cell
 de-differentiation and subsequent re-differentiation towards the two key anti-inflammatory
 programs, the TREG and Th2 pathways, thus creating a "hybrid" product. The hybrid phenotype
 inhibits inflammatory pathways operational in COVID-19, including modulation of multiple
 cytokines and chemokines, which attract inflammatory cells into tissue for initiation of
 multi-organ damage. The hybrid TREG and Th2 phenotype of RAPA-501-ALLO cells cross-regulates
 Th1 and Th17 populations that initiate hyperinflammation of COVID-19. RAPA-501 immune
 modulation occurs in a T cell receptor independent manner, thus permitting off-the-shelf cell
 therapy. Finally, in experimental models of viral pneumonia and ARDS, TREG cells mediate a
 protective effect on the lung alveolar tissue. Because of this unique mechanism of action
 that involves both anti-inflammatory and tissue protective effects, the allogeneic RAPA-501 T
 cell product is particularly suited for evaluation in the setting of COVID-19-related ARDS.
The first-in-human Phase 1 study component will evaluate two dose levels of RAPA-501-ALLO off
 the shelf cells in patients with COVID-19-related ARDS, with key endpoints of safety,
 biologic and potential disease-modifying effects. The randomized, double-blind,
 placebo-controlled Phase 2b study component will evaluate infusion of RAPA-501 ALLO off the
 shelf cells or a control infusion, with the primary endpoint assessing whether RAPA-501 cells
 reduce 30-day mortality.

 The COVID-19 pandemic is a disaster playing out with progressive morbidity and mortality. As
 of April 6th, 2021, an estimated 132.1 million people have contracted the virus and 2,866,000
 deaths have resulted globally. The United States has the highest totals with an estimated
 30.8 million people diagnosed and 556,000 deaths. The United States has the highest totals
 with an estimated 22.4 million people diagnosed and 375,000 deaths. In stages 1 and 2 of
 COVID-19, viral propagation within the patient is predominant. As such, therapeutic
 interventions focus on immune molecules (convalescent serum, monoclonal antibodies) and
 anti-viral medications (remdesivir). In marked contrast, the most severe and deadly form of
 COVID-19, stage 3, is driven not by viral propagation, but by an out-of-control immune
 response (hyperinflammation) caused by increases in immune molecules known as cytokines and
 chemokines. As such, therapeutic interventions for stage 3 disease focus on anti-inflammatory
 medications such as anti-cytokine therapy (anti-IL-6 drugs) or corticosteroid therapy.
 Unfortunately, such interventions do not address the full pathogenesis of stage 3 COVID-19,
 which includes hyperinflammation due to "cytokine storm" and "chemokine storm," tissue
 damage, hypercoagulation, and multi-organ failure (including lung, heart, kidney and brain).
 The pulmonary component of stage 3 disease includes acute respiratory distress syndrome
 (ARDS), which is a final-common-pathway of patient death due to a myriad of conditions,
 including pneumonia, sepsis, and trauma. There is a dire need for novel cellular treatments
 that can deliver both a broad-based immune modulation effect and a tissue regenerative
 effect, such as RAPA-501-ALLO off-the-shelf allogeneic hybrid TREG/Th2 Cells.

 The mechanism of fatal pneumonia in experimental murine coronavirus infection is mediated by
 innate inflammasome activation, a resultant robust infiltration of inflammatory monocytes and
 macrophages, and a subsequent increase in multiple pro-inflammatory cytokines and chemokines.
 Importantly, the CD4+ and CD8+ adaptive T cell response to experimental coronavirus infection
 can be either curative or disease propagating. Viral-induced pulmonary inflammation has also
 been evaluated in non-human primate models, which have confirmed that dysregulated immune
 activation during viral pneumonia involves T cell subset imbalance, a downstream
 monocyte-derived inflammatory cascade, and resultant epithelial cell injury. In humans,
 severity of viral-induced lower respiratory tract infection correlates with increased numbers
 of effector memory CD8+ T cells in the airway. As recently reviewed, human coronavirus
 infection represents an ongoing battle between virus and host, with the nature of the
 response dictating disease cure or alternatively, aggravated lung disease. Evidence exists
 that the adaptive immune system contributes to pulmonary inflammation during SARS-associated
 Coronavirus (SARS-CoV) disease: that is, bronchoalveolar fluid from such subjects had
 increased T cell numbers and increased Th1-associated molecules IL-12, IFN-gamma, and IP-10.
 This downstream adaptive T cell-mediated inflammatory response is driven in part by the
 SARS-Co-V protein viroporin 3a. Specifically, viroporin molecules activate the NLRP3
 inflammasome that links innate-to-adaptive inflammatory responses. Furthermore, both SARS-CoV
 and SARS-CoV-2 express an open-reading-frame ORF3a molecule, which also activate the NLRP3
 inflammasome.

 The nature of immunity during resolution of symptomatic COVID-19 infection has recently been
 reported, namely: emergence of antibody-secreting cells and CD4+ T follicular helper cells;
 increase in perforin- and granzyme-expressing CD8+ T cells; and relative lack of an increase
 in pro-inflammatory cytokines and chemokines. In marked contrast, patients with severe
 COVID-19 disease had greatly increased plasma levels of cytokines (including IL-2 and
 TNF-alpha) and chemokines (including IP-10 and MIP-1-alpha) (Huang et al., Lancet, 2020).
 Collectively, these results indicate that pro-inflammatory cytokine and chemokine responses
 that occur in severe COVID-19 is detrimental and that effective anti-inflammatory approaches
 may ultimately prove to be therapeutic. However, as previously detailed, the more advanced
 Stage 3 COVID-19 disease is characterized by an ARDS component, and cytokine storm, as such,
 novel approaches to treat the COVID-19 viral pneumonia should optimally incorporate both an
 anti-inflammatory element and a tissue protection/tissue repair element.

 Stage 3 COVID-19 carries an estimated 30-day mortality of over 50% in spite of ICU
 utilization, mechanical ventilation, and supportive care therapies to manage ARDS and
 multiorgan failure. Narrowly acting targeted anti-inflammatory approaches such as anti-IL-6
 therapeutics have not been particularly effective in stage 3 COVID-19 and the broad
 anti-inflammatory pharmaceutical approach of corticosteroid therapy, has only modestly
 tempered stage 3 disease in some studies. Cell therapy is also being evaluated in stage 3
 COVID-19, in particular, mesenchymal stromal cells (MSC) and now, with the current
 RAPA-501-ALLO protocol, regulatory T (TREG) cells. TREG therapy has a mechanism of action
 that includes a multi-faceted anti-inflammatory effect, which puts TREG therapy at the
 forefront of future curative therapy of a wide range of autoimmune and neurodegenerative
 diseases, plus transplant complications, such as graft-versus-host disease (GVHD) and graft
 rejection. In addition, TREG therapy can provide a tissue regenerative effect, which places
 TREG cell therapy at the lead of novel regenerative medicine efforts to repair a myriad of
 tissue-based diseases, such as diseases of the skin, muscle, lung, liver, intestine, heart
 (myocardial infarction) and brain (stroke). RAPA-501-ALLO off-the-shelf cell therapy offers
 this potential dual threat mechanism of action that incorporates both anti-inflammatory and
 tissue repair effects for effective treatment of COVID-19 and multiple lethal conditions.

 RAPA-501-ALLO cells are generated from healthy volunteers, cryopreserved, banked, and are
 then available for off-the-shelf therapy anytime. During manufacturing, T cells are
 "reprogrammed" ex vivo using a novel, patented 7-day two-step process that involves T cell
 de-differentiation and subsequent re-differentiation towards the two key anti-inflammatory
 programs, the TREG and Th2 pathways, thus creating a "hybrid" product. The hybrid phenotype
 inhibits inflammatory pathways operational in COVID-19, including modulation of multiple
 cytokines and chemokines, which attract inflammatory cells into tissue for initiation of
 multi-organ damage. The hybrid TREG and Th2 phenotype of RAPA-501-ALLO cells cross-regulates
 Th1 and Th17 populations that initiate hyperinflammation of COVID-19. RAPA-501 immune
 modulation occurs in a T cell receptor independent manner, thus permitting off-the-shelf cell
 therapy. Finally, in experimental models of viral pneumonia and ARDS, TREG cells mediate a
 protective effect on the lung alveolar tissue. Because of this unique mechanism of action
 that involves both anti-inflammatory and tissue protective effects, the allogeneic RAPA-501 T
 cell product is particularly suited for evaluation in the setting of Stage 3 COVID-19-related
 ARDS.

 In general, classical autoimmune disease, neurodegenerative disease, and viral-induced
 inflammatory disease are driven by predominance of Th1/Th17-type responses with a relative
 insufficiency of the counter-regulatory immune suppressive Th2 and TREG subsets. TREG cells,
 which are defined in part by their expression of FOXP3 transcription factor, have been
 extensively studied in experimental models for their capacity to modulate autoimmune disease,
 neurodegenerative disease, and transplantation complications, including graft-versus-host
 disease (GVHD) and graft rejection. Importantly, T cell production of IL-2 or exogenous IL-2
 administration drives lung inflammation during experimental viral infection; therefore, given
 the known role of TREG cells as a consumer of IL-2, there is a strong mechanistic rationale
 for a beneficial contribution of TREG cells during viral-driven lung inflammation.
 Furthermore, in an experimental murine models of virus-induced lung inflammation and lung
 injury, interventions that augmented TREG cell number and function accelerated the repair of
 lung injury. And, Th2 cells, which are defined in part by their expression of GATA3
 transcription factor, were described thirty years ago as a powerful counter-regulatory
 population to prevent Th1 cell predominance. It is important to note that clinical data
 indicates that maneuvers that increase immune suppressive cell populations, including TREG
 cells, can reduce severe inflammatory disease such as graft-versus-host disease without
 impairing anti-viral immunity. In addition, in both experimental models and clinical studies,
 an appropriate level of TREG cells can result in an overall improvement in pulmonary
 inflammation during viral bronchiolitis. Collectively, these findings indicate that T cells
 expressing a combined TREG/Th2 phenotype would predictably yield beneficial effects in the
 setting of viral-induced pulmonary inflammation and injury associated with severe Stage 3
 COVID-19 disease.

 Clinical trials have evaluated both TREG and Th2-type cells for various conditions, most
 prominently transplantation complications. In general, thymic-derived natural (n)TREG cells
 are thought to express a more stable phenotype than post-thymic induced (i)TREG cells; by
 comparison, iTREG cells can mediate more potent suppression. Nonetheless, both nTREG and
 iTREG cells are susceptible to differentiation plasticity, which creates concern that a
 potentially therapeutic TREG population might convert to pathogenic Th1/Th17 phenotypes in
 vivo. Ex vivo expanded (n)TREG cells were evaluated in the setting of allogeneic
 hematopoietic cell transplantation (HCT) using cord blood donors; more recently, the same
 research group has developed ex vivo expanded (i)TREG cell therapy to limit transplant
 complications. In addition, ex vivo expanded nTREG cells have been evaluated in the setting
 of type I diabetes mellitus; this clinical trial found that TREG therapy was safe and at
 least transiently effective in improving disease control. Furthermore, in the setting of
 amyotrophic lateral sclerosis (ALS), which is a disease propagated by a severe Th1-driven
 peripheral and central inflammatory response, a clinical trial of nTREG cell adoptive
 transfer identified that the intervention was safe and showed promise in terms of ALS disease
 amelioration. Finally, in a phase II study of rapamycin-resistant Th2 cell therapy in the
 setting of low-intensity allogeneic HCT, adoptive Th2 cell transfer was safe and associated
 with a shift towards Th2 polarization in vivo, preservation of donor engraftment,
 stabilization of mixed chimerism, a low rate of GVHD, and potent anti-tumor effects in
 patients with refractory hematologic malignancy. Collectively, these clinical trial results
 indicate that the adoptive transfer of TREG and Th2-type populations can be safely
 administered, even in the allogeneic HCT setting, and can mediate beneficial modulation of
 inflammatory conditions.

 Ex vivo manufacturing can be utilized to generate induced (i)TREG cells from the post-thymic
 pool of peripheral T cells. In the current protocol, the manufacturing method will focus upon
 mTOR inhibition, which is an established intervention that promotes the induction of TREG
 cells. In combination with mTOR inhibition, the culture system that is utilized incorporates
 cytokines that promote both a Th2 and a TREG phenotype, namely, IL-4, TGF-beta, and IL-2.
 Finally, the protocol will include a TREG/Th2 cell product comprised of both CD4+ and CD8+ T
 cell subsets, as these counter-regulatory T cell subsets express differential T cell receptor
 (TCR) repertoires and a diversity of effector mechanisms that can potentially enhance an
 anti-inflammatory effect. For RAPA-501 manufacture, peripheral blood mononuclear cells are
 collected from a steady-state apheresis and subjected to the following two-step culture
 intervention: in step 1, a severe starvation step results in T cell de-differentiation, which
 is realized through both selective media utilization and the addition of FDA-approved
 pharmaceutical agents that potently inhibit mTOR signaling; and in step 2, re-differentiation
 of T cells occurs using co-stimulation agents and Th2- and TREG-type polarizing cytokines.
 After 6-days in culture, the resultant TREG/Th2 population is cryopreserved in single-use
 aliquots at protocol-driven therapeutic doses. T cells of type II cytokine phenotype are
 characterized in part by their expression of the transcription factor GATA3 whereas
 regulatory T cell populations are identified in part by their expression of FOXP3
 transcription factor. At culture initiation, a very low frequency of T cells express either
 GATA3 or FOXP3. In contrast, the RAPA-501 cell product manufactured in the TREG/Th2 culture
 conditions expresses a high frequency of T cells that are either single-positive for GATA3,
 single-positive for FOXP3, or double-positive for both GATA3 and FOXP3. Importantly, this
 transcription factor profile is expressed in both manufactured CD4+ and CD8+ T cells. It is
 important to note that both CD4+ and CD8+ T cell populations with TREG function have been
 defined, including a CD8+ TREG population that potently suppresses GVHD; it is potentially
 advantageous to have both subsets represented in a therapeutic product because CD4+ and CD8+
 TREG cells utilize differential effector mechanisms.

 Regulatory T cell populations can suppress pathogenic effector T cell populations by several
 defined mechanisms, including through expression of CD39 and CD73 ectonucleotidase molecules,
 which act to hydrolyse pro-inflammatory ATP towards the immune suppressive adenosine
 substrate . Indeed, TREG cells that express CD39 possess increased suppressive function and
 have been associated with resolution of inflammatory bowel disease. Furthermore, suppressive
 function of human TREG cells is mediated in part by CD73. T cells manufactured in the
 TREG/Th2 culture condition have an increase in expression of the TREG-associated effector
 molecules, CD39 and CD73. In addition to the CD39/CD73 ectonucleotidases, TREG cell function
 has also been correlated with expression of CD103, which is an integrin that dictates
 epithelial lymphocyte localization. Indeed, CD103 and IL-2 receptor signaling cooperate to
 maintain immune tolerance in the gut mucosa; furthermore, CD103-expressing TREG cells are
 critical for amelioration of experimental chronic GVHD . T cells manufactured in the TREG/Th2
 culture condition have increased expression of the TREG effector molecule CD103.

 In experimental models, the efficacy of adoptive T cell therapy is dependent upon successful
 engraftment and in vivo T cell persistence. Importantly, the T cell differentiation state
 helps dictate in vivo persistence, with less differentiated cells having increased
 persistence. Murine rapamycin-resistant T cells, which expressed a T central memory (TCM)
 phenotype, had increased in vivo engraftment potential relative to control T cells. In
 addition, human rapamycin-resistant T cells also had increased engraftment in a
 human-into-murine model of xenogeneic graft-versus-host disease. T cells with reduced
 differentiation relative to the T effector memory (TEM) population have increased in vivo
 persistence and mediate increased in vivo effects, including the TCM subset, the naïve T cell
 subset, and more recently, the T stem cell memory (TSCM) subset. This relationship between T
 cell differentiation status and in vivo T cell function is relevant to TREG cells, as: (1)
 TREG cells of TCM phenotype were more effective at reducing experimental GVHD relative to
 TREG cells of TEM phenotype; and (2) TREG cells that expressed the stem cell marker CD150
 were highly effective for the prevention of stem cell graft rejection. T cells manufactured
 in the TREG/Th2 culture condition are enriched for cells having a reduced differentiation
 state consistent with a T stem cell subset, including expression of the CD150 marker.

 It is also important to assess the cytokine secretion profile of the manufactured RAPA-501
 cells. First, it is critical that the cell product is capable of IL-4 secretion, which is the
 driver cytokine for subsequent Th2 differentiation. Second, it is desirable that an
 adoptively transferred T cell population is capable of secreting IL-2, as this capacity
 indicates a progenitor function that permits T cells to expand more readily in vivo without
 the need for exogenous IL-2 . Finally, it is important that the RAPA-501 cell population has
 reduced secretion of the Th1- or Th17-type cytokines IFN-gamma, TNF-alpha, IL-17, and GM-CSF.
 The manufactured RAPA-501 cell product secretes IL-4 and IL-2 with minimal secretion of Th1-
 or Th17-type cytokines.

 Regulatory T cells can also be defined in part by their ability to suppress the proliferation
 or function of effector T cells. Importantly, manufactured TREG/Th2 cells potently suppress
 Th1/Tc1 cell secretion of multiple inflammatory cytokines, including IFN-gamma, GM-CSF, and
 TNF-alpha. To assess the mechanism of suppression, experiments were performed using the
 transwell assay, whereby effector T cells and RAPA-501 cells are separated by a filter that
 prevents cell-to-cell contact but allows cell communication by small soluble mediators such
 as cytokines. RAPA-501 cells acted in a TCR-independent manner to suppress the cytokine
 secretion capacity of effector T cells. Because no co-stimulation was provided to the
 transwell chamber containing RAPA-501 cells, RAPA-501 cells did not require co-stimulation to
 modulate inflammatory cytokine levels, including IL-2, IFN-gamma, GM-CSF, and TNF-alpha. The
 following cytokines and chemokines were reduced by RAPA-501 cells in this transwell assay,
 with relatively equal suppression mediated by CD4+ and CD8+ subsets of RAPA-501 cells: CCL1,
 CCL2, CCL7, CCL11, CCL13, CCL17, CCL20, CCL22, CCL26, CXCL1, CXCL10, CXCL11, CXCL12, IL-6,
 IFN-gamma, GM-CSF, and IL-10. The ability of TREG cells to consume IL-2 is a commonly
 described phenomenon, although previous studies identified the requirement of cell-to-cell
 contact for IL-2 consumption. As such, RAPA-501 cells are uniquely capable of modulating the
 level of multiple inflammatory cytokines in a contact-independent manner. These results
 suggest that RAPA-501 cells represent a suitable candidate for neutralization of multiple
 cytokines and chemokines associated with various diseases, including viral-induced lung
 inflammation. In light of this capacity of the RAPA-501 cell product to suppress T
 cell-mediated inflammation in a TCR-independent manner, RAPA-501 therapy is highly suitable
 for allogeneic, off-the-shelf treatment applications.

 Further experiments were performed to evaluate whether the RAPA-501 cell product might also
 regulate human CNS microglial cells, which are myeloid-derived cells that are analogous to
 the peripheral monocyte population. To evaluate whether the RAPA-501 cell product might
 modulate pro-inflammatory microglial cells in a contact-independent manner, the ability of
 RAPA-501 cells to reduce the inflammatory state of the microglial cell line HMC3 was tested
 in a transwell assay. RAPA-501 cells reduced the HMC3 cell secretion of the pro-inflammatory
 cytokines IL-6 and IFN-gamma and the pro-inflammatory chemokine IP-10 at the relatively low
 ratio of RAPA-501 cells to microglial cells of 1:40. These results demonstrate that the
 RAPA-501 product is capable of inhibiting cytokine and chemokine secretion from
 myeloid-derived populations in a contact- and TCR-independent manner, thereby providing a
 further rationale for allogeneic, off-the-shelf utilization of the RAPA-501 product.

 RAPA-501 cell product for stability of T cell phenotype was also evaluated. That is, it has
 been determined that a limiting factor of TREG cell therapy may be differentiation
 plasticity, for example, whereby TREG cells can be influenced by inflammatory cytokines to
 lose their TREG characteristics and adopt a Th1-type inflammatory state, which may then
 promote disease pathogenesis. To address this possibility, the RAPA-501 cell capacity to
 modulate T cell differentiation transcription factors after an extended culture interval that
 involved T cell co-stimulation, the absence of mTOR inhibitors, and the presence of the
 polarizing inflammatory cytokines IFN-alpha and IL-6 was studied. These experiments
 demonstrated that the RAPA-501 cell product had remarkable differentiation stability
 (continued expression of FOXP3 and GATA3 in CD4+ and CD8+ subsets; lack of up-regulation of
 TBET).

 In summary, RAPA-501 cells express a phenotype consistent with a regulatory T cell
 population, including: stable expression of the TREG and Th2 transcription factors FOXP3 and
 GATA3; expression of the TREG functional molecules CD39, CD73, and CD103; expression of a
 reduced state of T cell differentiation, including expression of the stem cell marker CD150;
 secretion of a Th2 pattern of cytokines with minimal secretion of Th1/Th17-type cytokines;
 functional suppressive capacity against both effector Th1/Tc1 cells and pro-inflammatory
 myeloid cells, including reduced levels of multiple inflammatory cytokines and chemokines;
 and a capacity to inhibit inflammatory effectors in a contact- and TCR-independent manner.
 Collectively, these characteristics of the RAPA-501 product predicts that this therapy
 represents a novel and promising candidate to treat COVID-19-related ARDS.

 This is a first-in-human phase 1/phase 2b study evaluating allogeneic RAPA-501 cell therapy
 in participants with COVID-19-related ARDS. Two phase 1 cohorts will be evaluated, namely, a
 low-dose Cohort 1 (40 x 10^6 cells/infusion) and a high-dose Cohort 2 (160 x 10^6
 cells/infusion); this phase 1 component will utilize dose-limiting-toxicity (DLT) as a
 primary endpoint. Provided that safety is demonstrated in the phase 1 study component, each
 RAPA-501 dose cohort can be evaluated in the randomized phase 2b component. In the phase 2b
 component, for each RAPA-501 dose level determined to be safe, patients will be randomized to
 receive RAPA-501 cells (n=19) or placebo (n=19). After infusion of either RAPA-501 cells or
 placebo, these randomized cohorts will continue on standard-of-care therapy (not
 protocol-driven). The primary endpoint of the phase 2b study is 30-day mortality, with the
 statistical goal of reducing mortality in RAPA-501 recipients relative to the randomized,
 placebo-control cohort.

 Study participants must be hospitalized patients with COVID-19-related ARDS, specifically:
 SARS-CoV-2 infection, as determined by RT-PCR or equivalent test; pulmonary infiltrate on
 radiologic examination; and a diagnosis of ARDS requiring intensive respiratory support
 including non-invasive ventilation such as high-flow nasal cannula or mechanical ventilation.
 The study consists of: (1) a study enrollment step (screening); and (2) after eligibility is
 confirmed, infusion of RAPA-501 cells will be performed. On Cohort 1, infusion of RAPA-501
 cells will be at a dose of 40 x 10^6 cells/infusion; three participants will be initially
 treated, with one week separating participants in this phase 1 component to evaluate for DLT,
 which will be defined as grade 3 or greater toxicity attributable to RAPA-501 cells within
 7-days of infusion. At any point that Cohort 1 therapy is deemed to be safe (either 0/3 or
 1/6 having a DLT), then Cohort 1 RAPA-501 therapy can be evaluated in the randomized phase 2b
 study component to address the primary study objective relating to 30-day mortality. At any
 point that Cohort 1 therapy is deemed to be safe, treatment on Cohort 2 can be initiated,
 which will evaluate the infusion of RAPA-501 cells at a dose of 160 x 10^6 cells/infusion. In
 the same manner as Cohort 1, if Cohort 2 therapy is deemed to be safe, Cohort 2 RAPA-501
 therapy can be evaluated in the randomized phase 2b study component to address the primary
 study objective relating to 30-day mortality. The study will be comprised of three main
 stages: (1) the above-detailed 30-day interval relating to the primary study objectives; (2)
 an extended, total 90-day interval to continue relatively intensive clinical monitoring of
 potential efficacy and safety endpoints; and (3) an extended, total 6-month interval to
 provide long-term clinical follow-up and to continue to monitor for laboratory parameters
 relating to immune and viral endpoints.
Inclusion Criteria:

 1. Male or female participants ≥ 18 years of age.

 2. Participants with SARS-CoV-2 infection, as defined by standard reverse transcriptase
 polymerase chain reaction (RT-PCR) assay or equivalent test.

 3. Must have pulmonary infiltrate on radiologic examination.

 4. Participant must have a clinical diagnosis of high-risk ARDS (as defined by a
 PaO2-to-FiO2 ratio of < 150 mm Hg) requiring intensive respiratory support, including
 non-invasive methods such as high-flow nasal cannula or mechanical ventilation.

 5. AST and ALT ≤ 3 x upper limit of normal (ULN).

 6. Consent must be given before performance of any study related procedure not part of
 standard medical care, with the understanding that consent may be withdrawn at any
 time without prejudice to future medical care. Informed consent can be obtained from
 healthcare proxy if the participant is unable to provide consent due to medical
 status.

 Exclusion Criteria:

 1. Active uncontrolled infection with a non-COVID-19 agent.

 2. Diagnosis of ARDS that is not considered to be high-risk, as defined by PaO2-to-FiO2
 ratio of ≥ 150 mm Hg.

 3. Any irreversible disease or condition for which 6-month mortality is estimated to be
 greater than 50%.

 4. End-stage liver disease with ascites unrelated to COVID-19 (Childs Pugh score > 12).

 5. Uncontrolled or significant cardiovascular disease, including but not limited to: (a)
 myocardial infarction, stroke, or transient ischemic attack within the past 30 days;
 (b) uncontrolled angina within the past 30 days; (c) any history of clinically
 significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or
 torsades de pointes; and (d) history of other clinically significant or uncontrolled
 heart disease, including: cardiomyopathy, congestive heart failure with New York Heart
 Association functional classification III or IV, myocarditis, pericarditis, or
 significant pericardial effusion.

 6. Known chronic kidney disease of Stage 4 or 5 severity or requiring hemodialysis.

 7. COVID-19-associated acute kidney injury requiring dialysis.

 8. HIV, hepatitis B, or hepatitis C seropositive.

 9. Patients with baseline QTc interval prolongation, as defined by repeated demonstration
 of a QTc interval >500 milliseconds.

 10. Patients on hydroxychloroquine (must discontinue at least 2-days before study entry).

 11. Pregnant or breastfeeding participants.

 12. Patients of childbearing age, or males who have a partner of childbearing potential,
 who are unwilling to practice contraception. Effective forms of birth control, which
 must be continued through the entire on-study 6-month interval, include: Abstinence;
 Intrauterine device (IUD); Hormonal (birth control pills, injections, or implants);
 Tubal ligation; or Vasectomy.

 13. Participants with malignancy requiring active therapy (not including non-melanoma skin
 cancer).

 14. Recipients of allogeneic hematopoietic cell transplant or solid organ transplant.

 15. History of WHO Class III or IV pulmonary hypertension.

 16. Severe thromboembolic disease, as defined by: administration of thrombolytic agents,
 insertion of vena cava filter, or pulmonary thrombectomy within one-week interval
 prior to screening.

 17. Participants may be excluded at the discretion of the PI or if it is deemed that
 allowing participation would represent an unacceptable medical or psychiatric risk.